KR20180047989A - Adsorbent for Capturing Carbon Dioxide Comprising Eutectic Mixture Promoter and Magnesium Oxide/Aluminium Oxide Composite and Method for Manufacturing Same - Google Patents

Abstract

The present invention relates to a magnesium oxide-based absorbent for collecting carbon dioxide and a method of preparing the same. More specifically, the present invention relates to a magnesium oxide-based absorbent for collecting carbon dioxide, which includes a eutectic mixture as an enhancer and a magnesium oxide/aluminum oxide complex, thereby having excellent cycle ability. According to the present invention, a problem of an existing magnesium oxide-based absorbent for collecting carbon dioxide, which exhibits excellent carbon dioxide adsorption performance at high temperature but a poor cycle performance, and subsequently, cannot be commercialized or used in the process is overcome. Thus, it is possible to provide the solid absorbent having remarkably improved cycle characteristics and the CO_2 adsorption performance that is not significantly lower than that of the existing technology. According to the magnesium oxide-based absorbent for collecting carbon dioxide including a magnesium oxide/aluminum oxide complex of the present invention, the structural change of the magnesium oxide is inhibited during repeated cycles of adsorption and regeneration, and the magnesium oxide-based absorbent has significantly improved cycle performance. Thus, the magnesium oxide-based absorbent can be effectively commercialized and used in a process in various industries.

Description

[0001] The present invention relates to an adsorbent for capturing carbon dioxide including a eutectic mixture enhancer and a magnesium oxide / aluminum oxide composite, and a method for producing the adsorbent,

The present invention relates to a magnesium oxide-based carbon dioxide adsorbent and a method for producing the same, and more particularly, to a magnesium oxide-based carbon dioxide adsorbent having an excellent cycle capacity by containing a eutectic mixture as a promoter and a magnesium oxide / And a method for producing the same.

Global energy demand is heavily dependent on fossil fuels, the primary fuel, and despite government policies to prevent climate change, fossil fuels are expected to continue to increase over the next decade. Combustion of fossil fuels is still the major cause of carbon dioxide emissions that contribute to global warming. The CO ₂ generation concentration in 2013 is 296 ppmv, a 40% increase over the mid-1800s and an average growth rate of 2 ppm / year in the last decade. In order for fossil fuels to remain central to the power sector, existing or future plants will have to successfully implement realistic, cost-effective CO ₂ capture technologies.

Carbon capture and sequestration (or storage) (CCS) is a physical process that involves collecting artificial carbon dioxide from its source and storing it before releasing it to the atmosphere. CCS is that reducing the CO ₂ emissions on a large scale by separating the CO ₂ is liquefied and stored, it is believed to be the most practical conditions for reducing greenhouse gases.

The success or failure of CCS technology development depends on successful research and development and demonstration from detailed technologies such as capture, compression, transport and storage of carbon dioxide, but CO ₂ capture technology accounts for about 80% of the total processing cost of CCS Research and development on CO ₂ capture technology is being actively carried out in developed countries such as the United States, Europe, and Japan.

CO ₂ adsorption using a liquid base medium such as aqueous amine has already been widely used and mature, while adsorption of CO ₂ using a solid medium is considered as a more realistic and low cost alternative to future CO ₂ capture technology. Unlike liquid adsorbents, solid adsorbents can be used in very wide temperature ranges from ambient temperature to 700 ° C, less waste is generated during the cycle, and consumed solid adsorbents can be easily handled without undue environmental precautions .

Various media such as zeolite, activated carbon, metal oxide, hydrotalcite, organic-inorganic hybrid and metal-organic framework have been considered as a solid medium for CO ₂ adsorption. In recent years, alkali metal oxides Based adsorbents have attracted attention. A variety of alkali metal oxides have been studied, among which magnesium oxide (MgO) based metal oxides have been evaluated as the most likely candidates due to suitable thermodynamic criteria, broad and adjustable basicity and base strength, and acceptable temperature ranges.

However, MgO-based sorbents lack resistance to aggregation or irreversible CO ₂ adsorption due to their continuous morphology and phase changes during the multiple adsorption / desorption processes under temperature-swing operation .

In recent years, MgO enhanced by eutectic mixture has been developed as a solid adsorbent for future CO ₂ capture due to excellent CO ₂ adsorption performance and speed. However, deterioration of CO ₂ adsorption performance due to changes in morphology and crystallinity occurring under multiple cycles of adsorption and regeneration still remains as a problem to be solved.

Under these circumstances, the present inventors confirmed that a novel carbon dioxide adsorbent containing a eutectic mixture promoting agent and a magnesium oxide / aluminum oxide composite oxide exerts excellent cycle characteristics and completed the present invention.

It is an object of the present invention to provide an adsorbent for capturing carbon dioxide comprising a promoter comprising a eutectic mixture and a magnesium oxide / aluminum oxide composite.

Another object of the present invention is to provide a method for producing an adsorbent for capturing carbon dioxide comprising a promoter containing a eutectic mixture and a magnesium oxide / aluminum oxide composite.

It is still another object of the present invention to provide a method for adsorbing carbon dioxide using the adsorbent.

It is still another object of the present invention to provide a method for regenerating the adsorbent.

One aspect of the present invention for achieving the above object is to provide an adsorbent for capturing carbon dioxide, which comprises an eutectic mixture-containing promoter and a magnesium oxide / aluminum oxide composite.

In the present invention, the eutectic mixture may be a mixture of two or more kinds of alkali nitrate salts. In particular, the eutectic mixture is a eutectic mixture of potassium nitrate (KNO ₃ ) and lithium nitrate (LiNO ₃ ) . The potassium nitrate and lithium nitrate may be mixed in a molar ratio of 1: 1 to 1: 4.

In the present invention, the eutectic mixture may be characterized by 20 to 45 wt% based on the weight of the total adsorbent.

In the present invention, the magnesium oxide / aluminum oxide composite may have a molar ratio of magnesium / aluminum of 4.0 to 5.0.

In another aspect of the present invention, there is provided a method for producing a eutectic mixture, comprising: mixing and pulverizing two or more alkali nitrate salts to prepare a eutectic mixture; Heating the eutectic mixture to a temperature above the eutectic temperature to homogenize the eutectic mixture; Cooling and homogenizing the eutectic mixture to obtain a eutectic mixture powder; Mixing the eutectic mixture powder with a magnesium oxide / aluminum oxide composite; And calcining the magnesium oxide / aluminum oxide composite mixed with the eutectic mixture powder. The present invention also provides a method for producing an adsorbent for capturing carbon dioxide.

In this method, the magnesium oxide / aluminum oxide composite is prepared by adding a metal precursor including an magnesium precursor and an aluminum precursor and an acid to a solvent and stirring the mixture; Evaporating the solvent to obtain a solid; And calcining the solid to obtain a magnesium oxide / aluminum oxide composite.

In the present invention, the homogenization step may be performed by heating at a temperature higher than the eutectic temperature of the eutectic mixture by 80 to 150 DEG C for 8 to 16 hours. The firing may be performed at 300 to 500 DEG C for 4 to 8 hours under a nitrogen gas atmosphere.

In the present invention, the magnesium precursor may be selected from magnesium hydroxide, magnesium nitrate, and magnesium acetate. The aluminum precursor may be selected from aluminum tetrabutoxide, aluminum isopropoxide, and aluminum nitrate. can do.

The firing in the production of the magnesium oxide / aluminum oxide composite may be performed at 500 to 900 ° C for 4 to 10 hours.

In the present invention, the acid may be selected from nitric acid, acetic acid, hydrochloric acid, sulfuric acid, and combinations thereof, and the solvent may be selected from ethanol, methanol, isopropyl alcohol, and combinations thereof .

Another aspect of the present invention is a method for producing a carbon dioxide adsorbent comprising the steps of: inducing melting of a eutectic mixture by heating an adsorbent for capturing carbon dioxide comprising a promoter comprising a eutectic mixture and a magnesium oxide / aluminum oxide composite to a eutectic temperature of the eutectic mixture; And introducing a carbon dioxide gas into the adsorbent to which the eutectic mixture is molten.

In the present invention, the adsorbent may be heated to 250 to 300 캜.

Another aspect of the present invention provides a regeneration method of an adsorbent for capturing carbon dioxide, characterized in that the adsorbent having been adsorbed by carbon dioxide is heated at 400 to 550 ° C for 5 to 20 minutes.

According to the present invention, conventional adsorbents for capturing magnesium oxide-based carbon dioxide overcome the problem that CO ₂ adsorption performance at high temperature is excellent but cyclic characteristics are poor so that they are not applicable to commercialization or processing, and CO ₂ adsorption performance It is possible to provide a solid adsorbent having significantly improved cycle characteristics without significantly falling off.

That is, the adsorbent for capturing carbon dioxide, which includes the eutectic mixture promoter and magnesium oxide / aluminum oxide composite according to the present invention, has excellent cycle characteristics by suppressing the structural change of MgO during the repeated cycle of adsorption and regeneration. It can be applied to the commercialization and the processing and can exert excellent effects.

1 is a MgO-Al ₂ O ₃ adsorbent, and the eutectic mixture -MgO-Al ₂ O represents an X- ray diffraction pattern (XRD) of the _three adsorbents.
2 shows a field emission scanning electron microscope (FE-SEM) image of eutectic mixture-MgO-Al ₂ O ₃ adsorbent.
Figure 3 is the ratio of the various MgO-based adsorbent - a graph showing the isothermal CO ₂ adsorption capacity.
FIG. 4 is a graph showing the isothermal CO ₂ adsorption performance of various MgO-based adsorbents.
FIG. 5 is a graph showing the CO ₂ adsorption performance of the eutectic mixture-MgO-Al ₂ O ₃ adsorbent of the present invention with temperature.
6 shows the in-situ XRD pattern of the eutectic mixture-Al ₂ O ₃ adsorbent -MgO invention.
7 is a graph showing the cycle characteristics of eutectic mixture-MagO adsorbent and eutectic mixture-MgO-Al ₂ O ₃ adsorbent.

Hereinafter, specific embodiments of the present invention will be described in detail.

The present invention relates to an adsorbent for capturing carbon dioxide comprising a promoter comprising a eutectic mixture and a magnesium oxide / aluminum oxide complex.

In the present invention, the term "promoter" means a substance contained in an adsorbent and acting as a catalyst or participating in a direct reaction to improve the adsorption activity of the adsorbent.

In the present invention, the term "eutectic mixture" refers to a solid of two or more kinds, meaning a solid melting point as if it were a kind of solid compound, and means a solid crystal mixture in which the liquid phase formed by melting shows the same composition as the original solid phase And it is a mixture of fine and heterogeneous crystals, but it is in the form of a seemingly homogeneous mixture.

In the present invention, when the eutectic mixture is used as an enhancer of magnesium oxide / aluminum oxide composite adsorbent, the CO ₂ adsorption ability is somewhat lost, but the structural change of MgO is suppressed during the repeated cycle of adsorption and regeneration, .

In the CO ₂ adsorbent composed of the active material (MgO), the eutectic mixture and the support (Al ₂ O ₃ ), the CO ₂ adsorption performance is maximized when the dispersibility of all the components increases. However, irreversible effects of the MgO phase and the morphology Stability is expected to decrease significantly due to changes. In addition, when the content of MgO is increased and the content of promoter and support is reduced, stability of the phase and morphology of MgO is increased, but the adsorption performance of CO ₂ is lowered. As such, stability and CO ₂ adsorption performance have been considered to exhibit a trade-off relationship with each other.

However, in the case of forming a magnesium / aluminum oxide (MgO-Al ₂ O ₃₎ as a composite using a eutectic mixture here as enhancers, CO ₂ adsorption performance is relatively while keeping not to greatly reduce CO ₂ absorption-regeneration It is possible to obtain a solid adsorbent having excellent cycle stability by effectively restraining the structural deformation of the adsorbent in the adsorbent.

In the magnesium oxide / aluminum oxide composite, the molar ratio of Mg / Al is preferably from 4.0 to 5.0, and most preferably from about 5.0 to Mg / Al. If the molar ratio of Mg / Al exceeds 5.0, excessive MgO can not be efficiently dispersed in the support together with the eutectic mixture, so that the continuous change of the morphology and the phase can not be suppressed, And problems such as breakage may occur.

The eutectic mixture according to the present invention is introduced into the surface of the magnesium oxide / aluminum oxide composite adsorbent and then heated to a melt or liquid phase by heating above the eutectic temperature, whereby the molten eutectic mixture is thereby spread over the surface of the composite adsorbent , And also penetrates into the pores of the adsorbent.

In the present invention, the eutectic mixture may be a mixture of two or more alkali nitrate salts. The alkali nitrate may be used in the form of two eutectic mixtures selected from sodium nitrate (NaNO ₃ ), lithium nitrate (LiNO ₃ ) and potassium nitrate (KNO ₃ ), and in the case of a binary eutectic mixture of potassium nitrate and lithium nitrate It is possible to exert the most excellent promoting effect as compared with the eutectic mixture of other combinations. A binary eutectic mixture of potassium nitrate and lithium nitrate Next, the combination of lithium nitrate and sodium nitrate exerts a superior promoting effect.

When the eutectic mixture is a binary eutectic mixture of potassium nitrate and lithium nitrate, it is preferable that the molar ratio of K: Li is in the range of 1: 1 to 1: 4 in view of CO ₂ adsorption performance, : 3 is more preferable.

In the present invention, the eutectic mixture is preferably contained in an amount of 20 to 45% by weight, more preferably 30 to 42.5% by weight, and most preferably 35 to 40% by weight based on the weight of the total adsorbent. When the content of the eutectic mixture is less than 20% by weight of the total adsorbent is CO ₂ adsorption performance enhancement effect is weak and, eutectic if the mixture content is more than 45% by weight, the excess of the eutectic mixture, covering the active sites of the adsorbent CO ₂ gas diffusion , The CO ₂ adsorption performance is rather rapidly reduced.

The eutectic mixture according to the present invention melts above the eutectic temperature to cover the surface of the magnesium oxide-based adsorbent in the form of a liquid and also penetrates into the pore structure of the adsorbent. In this way there is the CO ₂ will react at the interface of the eutectic mixture and the solid adsorbent in the liquid phase, which is a conventional absorbent CO ₂ gas and the gas-in place of that who collect the CO ₂ via a solid state reaction, solid - of the gas-liquid Efficiently generates a CO ₂ adsorption reaction in a triple-phase boundary (TPB), and also facilitates the activity of a bulk solid lattice. When the eutectic mixture melts above the eutectic temperature, the molten eutectic mixture acts as a solvent to dissolve the ionic bonds of Mg-O, helping CO ₂ adsorb to carbonation with magnesium carbonate.

Another aspect of the invention relates to a method of making an adsorbent comprising a promoter comprising a eutectic mixture and a magnesium oxide / aluminum oxide composite.

Specifically, the method for producing the adsorbent of the present invention comprises the steps of: preparing a magnesium oxide / aluminum oxide composite; Preparing a eutectic mixture powder; Mixing the eutectic mixture powder with a magnesium oxide / aluminum oxide composite; And calcining the magnesium oxide / aluminum oxide composite mixed with the eutectic mixture powder.

The step of preparing the magnesium oxide / aluminum oxide composite may include the steps of adding and stirring a metal precursor including an magnesium precursor and an aluminum precursor and an acid to a solvent, and stirring the mixture; Evaporating the solvent to obtain a solid; And calcining the solid to obtain a magnesium oxide / aluminum oxide composite.

The step of preparing the eutectic mixture powder may include mixing and pulverizing two or more kinds of alkali nitrate salts to prepare a eutectic mixture; Heating the eutectic mixture to a temperature above the eutectic temperature to homogenize the eutectic mixture; And cooling and re-grinding the homogenized eutectic mixture to produce a eutectic mixture powder.

In the present invention, the magnesium precursor may be a magnesium precursor known in the art, and a magnesium precursor selected from magnesium hydroxide, magnesium nitrate, and magnesium acetate may be used. Particularly, magnesium acetate is preferably used.

The aluminum precursor may be aluminum tetrabutoxide, aluminum isopropoxide, or aluminum nitrate. In particular, aluminum tetrabutoxide is preferably used.

In the present invention, the complexing reaction of the metal precursor is preferably performed under acidic conditions, and it is preferable to add an acid together with the metal precursor. The acid is preferably nitric acid, acetic acid, hydrochloric acid, sulfuric acid or a combination thereof, and is preferably used in an amount such that the pH is 4.0 to 6.0.

In the process according to the invention, the stirring is preferably carried out for a time sufficient for the metal precursor to form into a complex. In one embodiment of the present invention, the stirring is preferably performed for 4 to 10 hours.

In the present invention, the evaporation of the solvent can be carried out by using a suitable known method depending on the kind of the solvent. For example, in the case of ethanol, it is preferably carried out at 50 to 70 DEG C for 24 to 72 hours. Once the evaporation of the solvent is complete, a solid phase can be obtained.

The solid phase thus obtained can be firstly fired at 500 DEG C or higher to remove impurities such as moisture and volatile compounds adsorbed physically / chemically. The first firing may be performed by heating at 500 to 900 ° C for 4 to 10 hours, preferably by heating at 530 to 700 ° C for 4 to 6 hours. At this time, the heating can be carried out at a heating rate of 3 to 10 DEG C / min, preferably at a heating rate of 4 to 7 DEG C / min.

In the present invention, the eutectic mixture can be obtained by mixing and pulverizing two or more kinds of alkali nitrate salts and homogenizing them. The alkali nitrate may be used in the form of two or three kinds of eutectic mixtures selected from sodium nitrate (NaNO ₃ ), lithium nitrate (LiNO ₃ ) and potassium nitrate (KNO ₃ ) Mixture is most preferred. When the eutectic mixture is a binary eutectic mixture of potassium nitrate and lithium nitrate, it is preferable that the molar ratio of K: Li is in the range of 1: 1 to 1: 4 in view of CO ₂ adsorption performance, : 3 is more preferable.

In the present invention, the eutectic mixture is preferably contained in an amount of 20 to 45% by weight, more preferably 30 to 42.5% by weight, and most preferably 35 to 40% by weight based on the weight of the total adsorbent.

The homogenizing step of the eutectic mixture allows the eutectic mixture to be homogenized in the molten state by heating at a temperature higher than the eutectic temperature of the eutectic mixture by 80 to 150 DEG C for 8 to 16 hours.

The homogenized eutectic mixture is cooled to a solid phase, and is once again thoroughly pulverized and introduced into the magnesium oxide / aluminum oxide adsorbent in powder form. When a powdered eutectic mixture is placed on the surface of the solid adsorbent, secondary firing proceeds to allow the eutectic mixture to penetrate into the surface and pores of the adsorbent in a molten state. The secondary firing is preferably carried out under nitrogen gas at 300 to 500 ° C for 4 to 8 hours, preferably by heating at a heating rate of 1 to 5 ° C / min.

When the eutectic mixture is melted by secondary firing and spreads widely on the surface of the adsorbent in a liquid state and completely permeates into the pores, the solidified eutectic mixture enhanced magnesium oxide / aluminum oxide composite adsorbent can be prepared by cooling to room temperature again.

Another aspect of the present invention relates to a method of adsorbing carbon dioxide using an adsorbent comprising a eutectic mixture-containing promoter and a magnesium oxide / aluminum oxide composite.

The adsorbent of the present invention can initiate the adsorption of carbon dioxide when the eutectic mixture melts to a liquid phase above the eutectic temperature of the eutectic mixture. Accordingly, the method for adsorbing carbon dioxide using the eutectic mixture enhanced magnesium oxide / aluminum oxide composite adsorbent of the present invention comprises: inducing the melting of the eutectic mixture by heating the adsorbent above the eutectic temperature of the eutectic mixture; And introducing carbon dioxide gas into the adsorbent in which the eutectic mixture is molten.

The eutectic mixture-promoted magnesium oxide / aluminum oxide composite adsorbent of the present invention initiates adsorption of carbon dioxide at a temperature above the eutectic temperature of the eutectic mixture. By adjusting the eutectic temperature by controlling the type, composition and composition ratio of the eutectic mixture, Can be controlled. In the adsorbent of the present invention, the carbon dioxide adsorption initiation temperature is independent of the content of the eutectic mixture and depends only on the eutectic temperature of the eutectic mixture. In one embodiment of the invention, (K, Li) ₃ NO was confirmed that the Al ₂ O ₃ adsorbent--MgO superior carbon dioxide adsorption performance in the 250 to 300 ℃, in particular, the excellent CO ₂ adsorption at 300 ℃ Performance.

Another aspect of the present invention relates to a regeneration method of a eutectic mixture enhanced magnesium oxide / aluminum oxide composite adsorbent. The regeneration method may be carried out by heating the adsorbent with carbon dioxide adsorption at 400 to 550 ° C for 5 to 20 minutes, and preferably under an N ₂ atmosphere. In one embodiment of the present invention, the CO ₂ solid adsorbent according to the present invention has been desorbed from about 400 ° C, and it has been confirmed that desorption starts at a significantly lower temperature than the prior art solid adsorbent. This low temperature desorption is significant in that less energy can be consumed for regeneration of the CO ₂ adsorbent.

Hereinafter, the present invention will be described in more detail with reference to examples. It should be noted, however, that these examples are illustrative of some experimental methods and compositions in order to illustrate the present invention, and the scope of the present invention is not limited to these examples.

Example  One: EM - MgO - Al ₂ O ₃ Adsorbent manufacturing

Ethanol solution was added 4.92 g of aluminum tetrabutoxide and magnesium acetate was added so that the Mg / Al molar ratios were 3.0, 4.0 and 5.0, respectively. Then, 5 ml of nitric acid (70%) was added as a catalyst, and the mixture was stirred for 5 hours. And the solution was baked at 550 ℃ for 5 hours to obtain a MgO-Al ₂ O ₃ solid.

3.39 g of KNO ₃ and 1.61 g of LiNO ₃ were thoroughly mixed and pulverized to prepare a binary eutectic mixture. The binary eutectic mixture was melted at 225 DEG C for 12 hours to homogenize the melt. The homogenized nitrate mixture was cooled until it became a solid phase and completely pulverized once again to prepare a eutectic mixture powder.

30% by weight of the eutectic mixture powder was physically mixed with 70% by weight of MgO-Al ₂ O ₃ composite and then calcined at 400 ° C. for 4 hours to obtain a mixture of K, Li ) NO ₃ enhanced MgO-Al ₂ O ₃ composite adsorbent was prepared.

Example  2: X-ray diffraction pattern ( XRD ) analysis

The MgO-Al ₂ O ₃ complex and a (K, Li) NO ₃ - by using an X- ray diffraction pattern analyzer (D-Max2500-PC, Rigaku ) with respect to the enhanced-Al ₂ O ₃ composite X- MgO-ray diffraction The results of pattern analysis are shown in Figs. 1 (a) and 1 (b), respectively.

The XRD pattern of Figure 1 (a) it can be seen that the diffraction peaks corresponding to MgO and Al ₂ O ₃ exists on both sides. As the molar ratio of Mg / Al increased from 3.0 to 5.0, the diffraction peak shifted further toward MgO and the intensity of the diffraction peak of Al ₂ O ₃ decreased.

1 (b), diffraction peaks corresponding to LiNO ₃ and KNO ₃ exist in addition to the diffraction patterns of MgO and Al ₂ O ₃ , respectively. In this case, it can be seen that the intensity of the MgO-Al ₂ O ₃ peak is reduced as compared with the intensity determined in FIG. 1 (a). This means that all active species (Mg, O, Al, K) are evenly distributed throughout the sample.

In FIG. 1 (b), MgO shows a more pronounced peak as the molar ratio of Mg / Al increases, which means that the degree of crystallization increases and the adsorption of CO ₂ becomes more favorable.

Example 3: FE-SEM image analysis

(K, Li) NO ₃ -MgO-Al ₂ O ₃ adsorbents having a molar ratio of Mg / Al of 3.0, 4.0, and 5.0 prepared in Example 1 were subjected to field emission scanning electron microscopy (FE- SEM) images are shown in Figs. 2 (a) to 2 (c), respectively.

2 (a) to (c), it can be seen that the eutectic mixture-MgO-Al ₂ O ₃ sample exhibits a rough surface morphology. This is thought to be the result of the surface modification of the MgO-Al ₂ O ₃ while the MgO-Al ₂ O ₃ composite is coated with the eutectic mixture and then immediately activated by hot melting.

It can also be seen from Figs. 2 (a) to (c) that as the Mg / Al molar ratio increases, the size of the adsorbent particles increases. Such an increase in the size of the adsorbent particle means that the active material including the uniformly dispersed enhancer and the support is increased.

Example 4: ₂  Comparison of adsorption performance

4-1. Non-isothermal CO ₂  Adsorption test

It was measured using a thermogravimetric analyzer playback performance (TGA N-1000, SCINCO) - about 6 kinds of the solid adsorbent under non-isothermal CO ₂ adsorption. The results are shown in Fig.

(a) (K, Li) NO 3 -MgO

(b) NaNO ₃ -MgO

(c) (K, Li) NO 3 -MgO-Al 2 O 3

_{(d) MgO-Al 2 O} 3

(e) MgO

_{(f) NaNO 3 -MgO-Al} 2 O 3

Of the samples, (c) and (d) were those having Mg / Al = 5.0 as prepared in Example 1.

(a) (K, Li) NO ₃ -MgO was homogenized at a molar ratio of KNO ₃ : LiNO ₃ = 59: 41 and then mixed with MgO. (b) NaNO ₃ -MgO and (f) NaNO ₃ -MgO -Al ₂ O ₃ was prepared using a wet impregnation method using water as a solvent, and after drying, the cake was finished by calcining at 450 in an air atmosphere. At this time, the loading amount of NaNO ₃ was 20 wt%. (e) MgO was purchased from Daejeong Chemical and used.

As identifiable in Figure 3, the high CO ₂ as compared to a solid adsorbent ((a) to (c)) adsorbent ((d) and (e)) does not contain a promoter promoted by an alkali metal nitrate or a eutectic mixture Adsorption performance.

Interestingly, while the binary eutectic mixture can activate both MgO and MgO-Al ₂ O ₃ , NaNO ₃ activates only MgO, MgO-Al ₂ O ₃ does not activate at all, (D) and (f).

Eutectic adsorbent (c) according to the invention mixture -MgO-Al ₂ O ₃ exhibited the middle of the CO ₂ adsorption performance from the test _{adsorbent, (d) MgO-Al 2} O 3 adsorbent, and (e) MgO adsorbent And showed better CO ₂ adsorption performance.

4-2. Isothermal CO ₂  Adsorption test

(A) to (e) of the above samples were subjected to isothermal CO ₂ adsorption performance test using a thermogravimetric analyzer (TGA N-1000, SCINCO). The results are shown in FIG.

The isothermal CO ₂ adsorption performance test also shows that the solid adsorbents (a) to (c) promoted by the eutectic mixture or NaNO ₃ exhibit superior CO ₂ adsorption performance compared to the adsorbents (d) and (e) Respectively. In addition, the adsorbent (c) eutectic mixture -MgO-Al ₂ O ₃ exhibited the middle of the CO ₂ adsorption performance from the test _{adsorbent, (d) MgO-Al 2} O 3 adsorbent, and (e) according to the invention The adsorption performance of CO ₂ was better than that of MgO adsorbent.

4-3. CO according to temperature ₂  Adsorption performance

Figure 5 is a _{(K, Li) NO 3 -MgO} -Al 2 O 3 -5.0 isothermal CO ₂ adsorption 250 ℃ an adsorbent, respectively, at 275 ℃, 300 ℃, 350 ℃ and 375 ℃ for 60 minutes prepared in Example 1 The results of the test are shown.

In this experiment, the adsorption temperatures of CO ₂ were all set above the eutectic point of the eutectic mixture.

As can be seen from FIG. 5, the adsorption amount of CO ₂ according to the temperature showed a tendency to increase as the initial temperature rises from 250 ° C to 300 ° C. Then, the highest CO ₂ adsorption amount at 300 ° C. was 6.6 wt%, and then the adsorption performance was decreased with increasing temperature, and the adsorption performance was steeply decreased from 375 ° C. to 2.2 wt%.

It was confirmed that the adsorbent of (K, Li) NO ₃ -MgO-Al ₂ O ₃ -5.0 of the present invention exhibited the best CO ₂ adsorption performance at 250 to 300 ° C.

Example  5: in-situ XRD  analysis

In order to understand the reaction mechanism of the eutectic mixture-MgO-Al ₂ O ₃ adsorbent according to the present invention, in-situ XRD analysis was carried out using an X-ray diffractometer (D-Max-III C, Rigaku) Over the temperature range, respectively, in the flow of CO ₂ and N ₂ gases. The temperature was raised at a rate of 5 ° C / min and held at the measurement temperature for 2 minutes each. The results are shown in Figs. 6 (a) and 6 (b).

6 (a) and 6 (b), the peak intensity corresponding to the eutectic mixture gradually decreased with increasing temperature, but completely disappeared above 250 ° C. This proves that the eutectic mixture has transformed into an amorphous phase. On the other hand, the peaks corresponding to MgO-Al ₂ O ₃ are observed continuously, indicating that these phases have not changed.

In Fig. 6 (a), it is confirmed that two new characteristic peaks occur at a portion of 2θ = 32.76 ° and 53.46 °, as compared to Fig. 6 (b), indicating growth of MgCO ₃ phase. That is, it can be seen that MgCO ₃ starts to form from about 250 ° C. The peak intensity corresponding to MgCO ₃ increased with increasing temperature.

On the other hand, the peak intensity of MgCO ₃ decreased at 500 ° C. This means that 500 deg. C is the desorption initiation temperature.

As can be seen in the top graph of Fig. 6 (a), when cooling is carried out under a CO ₂ atmosphere, the final phase has diffraction peaks corresponding to MgO, MgCO ₃ and eutectic mixture.

On the other hand, in the case of Fig. 6 (b) in which the temperature was elevated in the N ₂ gas flow, it was not confirmed that a specific peak was generated, except that the peak of the eutectic mixture disappeared at 250 ° C or higher.

Example  6: Cycle characteristic test

In order to compare the cycle characteristics of the adsorbent of the present invention, the (K, Li) NO ₃ -MgO adsorbent showing the best CO ₂ adsorption performance in the CO ₂ adsorption performance test of Example 3 and the (K, Li) NO ₃ to 7 -MgO-Al ₂ O ₃ -5.0 measuring the CO ₂ absorption / desorption cycle profile of the adsorbent (a) and each was shown in (b).

In Fig. 7 (a), (K, Li) NO ₃ -MgO exhibited excellent adsorption of 34 wt% for 1 hour at 350 ° C in the first cycle. This is because the bulk MgO was activated in such a way that it melted in the molten eutectic mixture. However, effective declines in CO ₂ adsorption performance were confirmed after 17 consecutive cycles. This bulk MgO CO ₂ adsorption-stability by suffering notable structural deformation while undergoing a cycle of desorption is lowered due hayeotgi the loss of CO ₂ adsorption performance occurs. It was confirmed that the initial adsorption capacity, which was 34 wt.%, Dropped to 8.4 wt.% After 16 cycles, and it is expected that the adsorption capacity will further deteriorate in the subsequent cycles.

On the other hand, as can also check in 7 (b), the eutectic mixtures of the present invention, Al ₂ O ₃ adsorbent--MgO during consecutive cycles a single 11 showed a very stable CO ₂ adsorption capacity, but rather due to the active adsorption performance of MgO And the like. The CO ₂ adsorbent of the present invention can be expected to exhibit stable CO ₂ adsorption performance even in the additional cycle after the 11th cycle.

In addition, in FIG. 7 (b), the adsorption temperature and the desorption temperature of the eutectic mixture -MgO-Al ₂ O ₃ was reduced as compared to 7 (a) in FIG. 300 ℃ and 400 ℃ respectively. This means that the MgO-Al ₂ O ₃ composite can control the bonding properties between MgO and CO ₂ and that rapid structural changes can be controlled, which means that the regeneration of the adsorbent can be made more efficient.

From the above description, it will be understood by those skilled in the art that the present invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. In this regard, it should be understood that the above-described embodiments are to be considered in all respects as illustrative and not restrictive. The scope of the present invention should be construed as being included in the scope of the present invention without departing from the scope of the present invention as defined by the appended claims.

Claims (27)

A promoter comprising a eutectic mixture, and
Magnesium oxide / aluminum oxide complex
And an adsorbent for capturing carbon dioxide.
The method according to claim 1,
Characterized in that the eutectic mixture is a mixture of two or more alkali nitrate salts.
The method according to claim 1,
Wherein the eutectic mixture is a eutectic mixture of potassium nitrate (KNO ₃ ) and lithium nitrate (LiNO ₃ ).
The method of claim 3,
Wherein the potassium nitrate and lithium nitrate are mixed in a molar ratio of 1: 1 to 1: 4.
The method according to claim 1,
Characterized in that the eutectic mixture is contained in an amount of 20 to 45% by weight based on the weight of the total adsorbent.
The method according to claim 1,
Wherein the molar ratio of magnesium / aluminum is 4.0 to 5.0.
Mixing and pulverizing two or more alkali nitrate salts to prepare a eutectic mixture;
Heating the eutectic mixture to a temperature above the eutectic temperature to homogenize the eutectic mixture;
Cooling and homogenizing the eutectic mixture to obtain a eutectic mixture powder;
Mixing the eutectic mixture powder with a magnesium oxide / aluminum oxide composite; And
Calcining the magnesium oxide / aluminum oxide composite mixed with the eutectic mixture powder
Wherein the adsorbent for adsorbing carbon dioxide is an adsorbent.
8. The method of claim 7,
The magnesium oxide / aluminum oxide composite
Adding a metal precursor including a magnesium precursor and an aluminum precursor and an acid to the solvent and stirring the mixture;
Evaporating the solvent to obtain a solid; And
Calcining the solid to obtain a magnesium oxide / aluminum oxide composite
Wherein the adsorbent is produced from an adsorbent for adsorbing carbon dioxide.
8. The method of claim 7,
Wherein the alkali nitrate salt is selected from sodium nitrate (NaNO ₃ ), lithium nitrate (LiNO ₃ ) and potassium nitrate (KNO ₃ ).
8. The method of claim 7,
Wherein the eutectic mixture is a mixture of potassium nitrate and lithium nitrate in a molar ratio of 1: 1 to 1: 4.
8. The method of claim 7,
Wherein the eutectic mixture comprises 20 to 45% by weight based on the weight of the total adsorbent.
8. The method of claim 7,
Wherein the homogenization step is carried out by heating at a temperature of 80 to 150 DEG C higher than the eutectic temperature of the eutectic mixture for 8 to 16 hours.
8. The method of claim 7,
Wherein the calcination is carried out at 300 to 500 DEG C for 4 to 8 hours under nitrogen gas.
9. The method of claim 8,
Wherein the magnesium precursor is selected from magnesium hydroxide, magnesium nitrate, and magnesium acetate.
9. The method of claim 8,
Wherein the aluminum precursor is selected from aluminum tetrabutoxide, aluminum isopropoxide and aluminum nitrate.
9. The method of claim 8,
Wherein the calcination is carried out at 500 to 900 占 폚 for 4 to 10 hours.
9. The method of claim 8,
Wherein the acid is selected from nitric acid, acetic acid, hydrochloric acid, sulfuric acid, and combinations thereof.
9. The method of claim 8,
Wherein the solvent is selected from the group consisting of ethanol, methanol, isopropyl alcohol, and combinations thereof.
9. The method of claim 8,
Wherein the magnesium precursor and the aluminum precursor are added so that the molar ratio of magnesium / aluminum is 4.0 to 5.0.
Heating the eutectic mixture to a temperature above the eutectic temperature of the eutectic mixture, the promoter comprising a eutectic mixture and a magnesium oxide / aluminum oxide composite; And
Introducing carbon dioxide gas into the adsorbent in which the eutectic mixture is molten
Gt;
21. The method of claim 20,
Wherein the adsorbent is heated to 250 to 300 占 폚.
21. The method of claim 20,
Wherein the eutectic mixture is a eutectic mixture of potassium nitrate and lithium nitrate.
23. The method of claim 22,
Wherein said potassium nitrate and lithium nitrate are mixed in a molar ratio of 1: 1 to 1: 4.
A regeneration method of an adsorbent for capturing carbon dioxide comprising a promoter comprising a eutectic mixture and a magnesium oxide / aluminum oxide complex,
Wherein the adsorbent having been adsorbed by carbon dioxide is heated at 400 to 550 DEG C for 5 to 20 minutes.
25. The method of claim 24,
Wherein the heating is carried out in an atmosphere of N ₂ .
25. The method of claim 24,
Wherein the eutectic mixture is a eutectic mixture of potassium nitrate and lithium nitrate.
27. The method of claim 26,
Wherein the potassium nitrate and lithium nitrate are mixed in a molar ratio of 1: 1 to 1: 4.

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