KR102046794B1 - Adsorbent for Capturing Carbon Dioxide Comprising Eutectic Mixture Promoter and Magnesium Oxide/Titanium Dioxide Composite and Method for Manufacturing Same - Google Patents

Abstract

The present invention relates to a magnesium oxide-based carbon dioxide capture adsorbent and a method for manufacturing the same, and more particularly, to a magnesium oxide-based carbon dioxide capture adsorbent having a eutectic mixture as an enhancer and a magnesium oxide / titanium oxide composite And it relates to a manufacturing method thereof.
According to the present invention, the conventional magnesium oxide-based carbon dioxide capture adsorbents have excellent CO ₂ adsorption performance at high temperature but have poor cycle characteristics, and thus are difficult to be applied to commercialization or process, and CO ₂ adsorption performance is higher than that of the prior art. It is possible to provide solid adsorbents with significantly improved cycle characteristics without significant dropping.

Description

Adsorbent for Capturing Carbon Dioxide Comprising Eutectic Mixture Promoter and Magnesium Oxide / Titanium Dioxide Composite and Method for Manufacturing Same} including eutectic mixture enhancer and magnesium oxide / titanium oxide composite

The present invention relates to a magnesium oxide-based carbon dioxide capture adsorbent and a method for manufacturing the same, and more particularly, to a magnesium oxide-based carbon dioxide capture adsorbent having a eutectic mixture as an enhancer and a magnesium oxide / titanium oxide complex And it relates to a manufacturing method thereof.

Global energy demand relies heavily on fossil fuels, the primary fuel, and fossil fuels are expected to continue to increase in the coming decade despite government policies to prevent climate change. The burning of fossil fuels is still the largest source of carbon dioxide emissions that contribute to global warming. CO ₂ generated a concentration of 2013, as 296ppmv, which showed a 40% increase of more, and the last 10 years the average growth rate of 2ppm / year as compared to the mid-1800s. In order for fossil fuels to remain central in the power sector, existing or new plants will have to successfully implement realistic and cost-effective CO ₂ capture technology.

Carbon capture and sequestration (or storage) (CCS) is a physical process that involves collecting artificial carbon dioxide from its source and storing it prior to release into 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 of CCS technology will capture carbon dioxide, compressed, transported, and although dependent on the successful research, development and demonstration from the detailed component technologies such as storage, particularly because it accounts for about 80% of the CO ₂ capture technologies CCS overall treatment costs R & D on CO ₂ capture technology is actively underway in developed countries such as the US, Europe, and Japan.

CO ₂ adsorption with liquid base media such as aqueous amines is already widely used and mature, while CO ₂ adsorption with solid media is being considered as a future CO ₂ capture technology as a more realistic and low cost alternative. Unlike liquid adsorbents, solid adsorbents can be used over a very wide temperature range from ambient to 700 ° C, resulting in less waste during the cycle, and consumed solid adsorbents can be easily disposed of without excessive environmental precautions. .

Zeolite, activated carbon, metal oxides, hydrotalcites, organic-inorganic hybrids and metal-organic frameworks are considered as solid media for CO ₂ adsorption. Recently, alkali metal oxides have been considered. Adsorbents based on the spotlight are attracting attention. Although studies have been made on various alkali metal oxides, magnesium oxide (MgO) based metal oxides are among the most promising candidates due to suitable thermodynamic criteria, wide and adjustable basicity and base strength, and acceptable temperature range.

Reaction because of the ability to dissolve both the (adsorbent and absorbate complex), enhanced by the molten salt, such as a molten mixture that can be active ingredients are ionized or activated MgO is a next generation of the adsorbent due to the CO ₂ adsorption amount and speed considerations It is becoming. Numerous CO ₂ carriers (alkaline / alkaline carbonates) and enhancers (alkaline / alkylate nitrates) and combinations thereof have been investigated in the field of adsorbents.

However, suitable enhancers and / or catalysts for MgO have not yet been developed due to the high stability of carbonates (ie MgCO ₃ ). Carbonation of MgO changes the crystal structure from cubic MgO to trigonal MgCO ₃ , which causes the collapse of MgO reactivity due to aggregation. Efforts to limit the higher reactivity of MgO are still underway.

Against this background, the present inventors have completed the present invention by confirming that a novel carbon dioxide capture adsorbent including a eutectic mixture enhancer and a magnesium oxide / titanium oxide composite oxide exhibits excellent cycle characteristics.

It is an object of the present invention to provide an adsorbent for carbon dioxide capture comprising an enhancer comprising a eutectic mixture and a magnesium oxide / titanium oxide complex.

It is another object of the present invention to provide a method for preparing a carbon dioxide capture adsorbent comprising an enhancer including a eutectic mixture and a magnesium oxide / titanium oxide complex.

Still another object of the present invention is to provide a carbon dioxide adsorption method using the adsorbent.

Another object of the present invention is to provide a method for regenerating the adsorbent.

One aspect of the present invention for achieving the above object, there is provided an enhancer comprising a eutectic mixture and an adsorbent for carbon dioxide capture comprising a magnesium oxide / titanium oxide complex.

In the present invention, the eutectic mixture may be characterized in that a mixture of alkali nitrates of two or more, in particular, a eutectic mixture of potassium nitrate (KNO _3), and lithium nitrate to characterized in that the eutectic mixture of (LiNO ₃₎ Can be. 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 in that it comprises 20 to 40% by weight based on the total weight of the adsorbent.

In the present invention, the composite may be characterized in that it contains 2 to 10% by weight of TiO ₂ .

Another aspect of the present invention is to prepare a eutectic mixture by mixing and grinding two or more alkali nitrates; Homogenizing the eutectic mixture by heating above the eutectic temperature; Cooling and regrinding the homogenized eutectic mixture to prepare a eutectic mixture powder; Mixing the eutectic mixture powder with the magnesium oxide / titanium oxide complex; And calcining the magnesium oxide / titanium oxide composite mixed with the eutectic mixture powder.

In the method, the magnesium oxide / titanium oxide composite may include adding and stirring a metal precursor and an acid including a magnesium precursor and a titanium precursor to a solvent; Evaporating the solvent to obtain a solid; And calcining the solid to obtain a magnesium oxide / titanium oxide composite.

In the present invention, the homogenization step may be carried out by heating for 8 to 16 hours at a temperature 80 to 150 ℃ higher than the eutectic temperature of the eutectic mixture. In addition, the calcination may be characterized in that it is carried out for 4 to 8 hours at 300 to 500 ℃ under nitrogen gas.

In the present invention, the magnesium precursor may be selected from magnesium hydroxide, magnesium nitrate and magnesium acetate, the titanium precursor is titanium tetrabutoxide (titanium tetrabutoxide), titanium propoxide (titanium propoxide), titanium It may be characterized in that it is selected from isopropoxide (titanium isopropoxide), titanium methoxide (titanium methoxide) and titanium ethoxide (titanium ethoxide).

Firing in the preparation of the magnesium oxide / titanium 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. .

Still another aspect of the present invention provides a method for preparing a eutectic mixture, comprising: inducing melting of the eutectic mixture by heating an adjuvant including a eutectic mixture and an adsorbent for capturing carbon dioxide, including a magnesium oxide / titanium oxide complex, above the eutectic temperature of the eutectic mixture; And introducing a carbon dioxide gas into the adsorbent in which the eutectic mixture is melted.

In the present invention, the method may be characterized in that the adsorbent is heated to 250 to 325 ° C in 100% CO ₂ atmosphere.

In the present invention, the method may be characterized in that in a CO ₂ atmosphere of 30% or less, heating the adsorbent to 200 to 300 ℃.

Another aspect of the present invention provides a method for regenerating an adsorbent for collecting carbon dioxide, wherein the adsorbent on which carbon dioxide adsorption is completed is heated at 400 to 550 ° C. for 5 to 20 minutes.

According to the present invention, the conventional magnesium oxide-based carbon dioxide capture adsorbents have excellent CO ₂ adsorption performance at high temperature but have poor cycle characteristics, and thus are difficult to be applied to commercialization or process, and CO ₂ adsorption performance is higher than that of the prior art. It is possible to provide solid adsorbents with significantly improved cycle characteristics without significant dropping.

That is, since the eutectic mixture enhancer and the carbon dioxide capture adsorbent including the magnesium oxide / titanium oxide complex according to the present invention have very excellent cycle characteristics by suppressing the structural change of MgO during repeated cycles of adsorption and regeneration, It is possible to exert an excellent effect by being applied to commercialization and process.

Figure 1 (a) shows the results of X-ray diffraction pattern analysis of the MT _(x) adsorbent.
Figure 1 (b) shows the results of X-ray diffraction pattern analysis of the EM _(0.3) MT _(x) adsorbent.
Figure 2 (a) shows the N ₂ adsorption-desorption isotherm and pore distribution curve of the MT _(x) adsorbent.
2 (b) shows N ₂ adsorption-desorption isotherms and pore distribution curves of EM _(0.3) MT _(x) adsorbents.
3 shows a CO ₂ absorption performance of the EM _(0.3) MT _(x) samples having different MgO content.
Figure 4 (a) shows the amount of CO ₂ adsorption with temperature under 100% CO ₂ .
Figure 4 (b) shows the amount of CO ₂ adsorption with temperature under 15% CO ₂ .
5 (a) shows the cycle characteristics of the EM-MgO adsorbent.
5 (b) shows the cycle characteristics of the EM _(0.3) MT _(0.98) adsorbent.
5 (c) shows the cycle characteristics of the EM _(0.3) MT _(0.95) adsorbent.
6 (a)-(f) show FE-SEM images of EM _(0.3) MT _(0.95) adsorbents before CO 2 adsorption and after 11 cycles.
7 (a)-(f) show FE-TEM images of EM _(0.3) MT _(0.95) adsorbents before CO 2 adsorption and after 11 cycles.

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

The present invention relates to an enhancer comprising a eutectic mixture and an adsorbent for carbon dioxide capture comprising a magnesium oxide / titanium oxide complex.

In the present invention, "promoter" means a substance which is included in the adsorbent and acts like a catalyst or participates in a direct reaction to improve the adsorption activity of the adsorbent.

In the present invention, "eutectic mixture" means a solid crystal mixture of two or more solids, which exhibits a constant melting point as if it is a kind of solid compound, and the liquid phase formed by melting shows the same composition as the original solid phase. And fine heterogeneous crystals are mixed but seemingly uniform.

In the present invention, when the eutectic mixture is used as an enhancer for the magnesium oxide / titanium oxide composite adsorbent, the CO ₂ adsorption capacity is somewhat lost, but the structural change of MgO is suppressed during the repeated cycles of adsorption and regeneration, resulting in very good cycle characteristics. I confirmed that I had.

In the CO ₂ adsorbent consisting of the active substance (MgO), eutectic mixture and support (TiO ₂ ), the increase in dispersibility of all components increases the CO ₂ adsorption performance to the maximum, but due to the irreversible change of phase and morphology of MgO The stability is expected to decrease significantly. In addition, when the MgO content is increased and the content of the enhancer and the support is reduced, the stability and the phase and morphology of the MgO are greatly increased, but the CO ₂ adsorption performance is lowered. In this way, the stability and CO ₂ adsorption performance is another trade-off has been considered to represent a (trade-off) relationship.

Conventional eutectic-enhanced MgO adsorbents exhibit excellent CO ₂ adsorption performance by highly ionized MgO species, but cycle performance has been disadvantageous. It is believed that this is because highly active MgO species rapidly structurally relocate from cubic MgO to trigonal MgO. Although CO ₂ desorption can be promoted by dissolution of both Mg ²⁺ and CO ₃ ^2- ions at high temperatures, it is believed that the lattice deformation during the adsorption-desorption process is fast.

In general, desorption energy should be minimized to make regeneration easier. However, due to the formation of stable MgCO ₃ , the resulting species undergo greater distortion during the desorption step. One limitation to solve this problem is that carbonation of MgO is carried out at higher temperature ranges to form various base points of different strengths (ie weak base, heavy base, strong base). It is clear that the desorption energy will change depending on the strength of the base points, but it is difficult to produce similar kinds of base points in MgO. However, the interaction between dissolved Mg ²⁺ and CO ₃ ^2- species can be controlled by adding a third species that does not react with MgO.

In the present invention, when magnesium oxide / titanium oxide (MgO-TiO ₂ ) is formed as a composite and a eutectic mixture is used as the enhancer, the CO ₂ adsorption-regeneration process is maintained while maintaining the CO ₂ adsorption performance not relatively reduced. It has been found that a solid adsorbent with very good cycle stability can be obtained by efficiently suppressing structural deformation of the adsorbent at.

The magnesium oxide / titanium oxide composite is preferably composed of MgO and TiO ₂ , where MgO is contained in an amount of 90 to 98% by weight, and TiO ₂ is preferably contained in an amount of 2 to 10% by weight. If the content of TiO2 is less than 2% by weight, the content of Ti is too small to exhibit the desired cycle characteristics, and if it is more than 10% by weight, the content of Mg is too small to achieve the required amount of CO ₂ capture. In one embodiment of the present invention, it was confirmed that the adsorbent composed of 95% by weight of MgO and 5% by weight of TiO ₂ exhibited very good cycle characteristics.

The eutectic mixture according to the present invention is introduced into the surface of the magnesium oxide / titanium oxide composite adsorbent and then heated to a eutectic temperature or higher to become a melt, that is, a liquid phase. The molten eutectic mixture thus spreads widely on the surface of the composite adsorbent. And also penetrate into the pores of the adsorbent.

In the present invention, the eutectic mixture may be a mixture of two or more alkali nitrates. 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 ), in the case of a binary eutectic mixture of potassium nitrate and lithium nitrate The best promotion effect can be achieved over other combinations of eutectic mixtures. Following the binary eutectic mixture of potassium nitrate and lithium nitrate, the combination of lithium nitrate and sodium nitrate exerts an excellent enhancement effect.

When the eutectic mixture is a binary eutectic mixture of potassium nitrate and lithium nitrate, it is preferable from the viewpoint of CO ₂ adsorption performance that the molar ratio of K: Li satisfies the range of 1: 1 to 1: 4, and 1: 1.5 to 1 It is more preferable to mix in ratio of 3: 3.

In the present invention, the eutectic mixture is preferably contained 10 to 50% by weight, more preferably 20 to 40% by weight, and most preferably 25 to 35% by weight relative to the total weight of the adsorbent. When the eutectic mixture content is less than 10% by weight of the total adsorbent, the effect of improving CO ₂ adsorption performance is weak, and when the eutectic mixture content exceeds 50% by weight, the excess eutectic mixture covers the active point of the adsorbent and the CO ₂ gas diffusion as they create a thick layer of CO ₂ adsorption performance it is rather sharply reduced to interfere with.

The eutectic mixture according to the invention melts above the eutectic temperature to cover the surface of the magnesium oxide-based adsorbent in the form of a liquid and also penetrate 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 generate CO ₂ adsorption reactions at the triple-phase boundary (TPB) and also facilitate the activity of the 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 to adsorb CO ₂ and carbonate it to magnesium carbonate.

Another aspect of the invention relates to a process for preparing an adsorbent comprising a magnesium oxide / titanium oxide complex and an enhancer comprising a eutectic mixture.

Specifically, the manufacturing method of the adsorbent of the present invention comprises the steps of preparing a magnesium oxide / titanium oxide complex; Preparing a eutectic powder; Mixing the eutectic mixture powder with the magnesium oxide / titanium oxide complex; And calcining the magnesium oxide / titanium oxide composite mixed with the eutectic mixture powder.

Here, the preparing of the magnesium oxide / titanium oxide complex may include adding and stirring a metal precursor and an acid including a magnesium precursor and a titanium precursor to a solvent; Evaporating the solvent to obtain a solid; And calcining the solid to obtain a magnesium oxide / titanium oxide composite.

In addition, the step of preparing the eutectic mixture powder may include the steps of mixing and grinding two or more alkali nitrates to produce a eutectic mixture; Homogenizing the eutectic mixture by heating above the eutectic temperature; And cooling and regrinding the homogenized eutectic mixture to produce a eutectic mixture powder.

In the present invention, the magnesium precursor may use a magnesium precursor known in the art, and may use a magnesium precursor selected from magnesium hydroxide, magnesium nitrate and magnesium acetate. In particular, it is preferable to use magnesium acetate.

In addition, the titanium precursor is titanium tetrabutoxide, titanium propoxide, titanium isopropoxide, titanium methoxide, titanium ethoxide, or the like. It is possible to use, in particular, it is preferred to use titanium tetra butoxide.

In the present invention, the complexing reaction of the metal precursor is preferably performed under acidic conditions, and for this purpose, 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 agitation is preferably carried out for a sufficient time for the metal precursor to form a composite. In one embodiment of the present invention, the stirring is preferably performed for 4 to 10 hours.

In the present invention, evaporation of the solvent can be carried out using a known method appropriate to the type of solvent. For example, in the case of ethanol, it is preferably carried out at 50 to 70 ℃ for 24 to 72 hours. Once the evaporation of the solvent is complete a solid phase can be obtained.

The solid phase thus obtained may be subjected to primary firing at 500 ° C. or higher to remove impurities such as water and volatile compounds adsorbed physically and chemically. The primary firing may be performed by heating at 500 to 900 ° C. for 4 to 10 hours, and preferably by heating at 530 to 700 ° C. for 4 to 6 hours. At this time, the heating may be performed at a temperature increase rate of 3 to 10 ℃ / min, preferably 4 to 7 ℃ / min.

In the present invention, the eutectic mixture can be obtained by mixing, grinding and homogenizing two or more alkali nitrates. The alkaline nitrate is sodium nitrate (NaNO _3), lithium nitrate (LiNO ₃₎ and potassium nitrate (KNO ₃₎ can be used in the form of a eutectic mixture of two or three selected from 2 won eutectic of potassium nitrate and lithium nitrate Most preferred is a mixture. When the eutectic mixture is a binary eutectic mixture of potassium nitrate and lithium nitrate, it is preferable from the viewpoint of CO ₂ adsorption performance that the molar ratio of K: Li satisfies the range of 1: 1 to 1: 4, and 1: 1.5 to 1 It is more preferable to mix in ratio of 3: 3.

In the present invention, the eutectic mixture is preferably contained 10 to 50% by weight, more preferably 20 to 40% by weight, and most preferably 25 to 35% by weight relative to the total weight of the adsorbent.

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

The homogenized complete eutectic mixture is cooled to a solid phase, and then once again completely pulverized and introduced into the magnesium oxide / titanium oxide adsorbent in the form of a powder. When the eutectic mixture in powder form is located on the surface of the solid adsorbent, secondary firing is performed to allow the eutectic mixture to penetrate into the surface and pores of the adsorbent in a molten state. The secondary firing is preferably performed at 300 to 500 ° C. for 4 to 8 hours under nitrogen gas, and is preferably performed by heating at a temperature increase rate of 1 to 5 ° C./minute.

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

Another aspect of the invention relates to a method for adsorbing carbon dioxide using an enhancer comprising a eutectic mixture and an adsorbent comprising a magnesium oxide / titanium oxide complex.

The adsorbent of the present invention may initiate carbon dioxide adsorption when the eutectic mixture melts above the eutectic temperature of the eutectic mixture and becomes a liquid phase. Therefore, the adsorption method of carbon dioxide using the eutectic mixture-enhanced magnesium oxide / titanium oxide composite adsorbent of the present invention comprises the steps of inducing 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 melted.

In the eutectic mixture-enhanced magnesium oxide / titanium oxide composite adsorbent of the present invention, carbon dioxide adsorption is initiated above the eutectic temperature of the eutectic mixture. Can be controlled. In the adsorbent of the present invention, the carbon dioxide adsorption onset temperature is independent of the content of the eutectic mixture and depends only on the eutectic temperature of the eutectic mixture.

Further, it is preferable to set different absorption start temperature in accordance with the CO ₂ concentration. In one embodiment of the present invention, (K, Li) NO ₃ -MgO-TiO ₂ adsorbent exhibits excellent carbon dioxide adsorption performance at 250 to 325 ° C. under 100% CO ₂ atmosphere and the highest CO ₂ adsorption performance at 300 ° C. It was confirmed that the present invention exhibits excellent adsorption performance at 200 to 250 ° C. under 15% CO ₂ atmosphere.

Another aspect of the invention relates to a process for regenerating a eutectic mixture-enhanced magnesium oxide / titanium oxide composite adsorbent. The regeneration method may be performed by heating the adsorbent in which carbon dioxide adsorption is completed for 5 to 20 minutes at 400 to 550 ° C., preferably under N ₂ atmosphere. In one embodiment of the present invention, the CO ₂ solid adsorbent according to the present invention was confirmed that the desorption proceeds from about 450 ° C., so that desorption starts at a significantly lower temperature than the solid adsorbent of the prior art. This low temperature desorption is significant in that less energy may be consumed for the regeneration of the CO ₂ adsorbent.

Hereinafter, the present invention will be described in more detail with reference to the following examples. However, these examples show some experimental methods and compositions in order to illustrate the present invention by way of example, the scope of the present invention is not limited to these examples.

Preparation Example 1 MgO-TiO ₂ Sorbent manufacturers

1 g of HO (CH ₂ CH ₂ O) ₂₀ (CH ₂ CH (CH ₃ ) O) ₇₀ (CH ₂ CH ₂ O) ₂₀ H (Pluronic P ₁₂₃ , Sigma-Aldrich) as a flexible template triblock copolymer 94.5%, three thousand chemicals) to 50ml Add and dissolve for 4 hours. Then magnesium nitrate hexahydrate (Mg (NO ₃ ) ₂ 6H ₂ O) (99%, Sigma-Aldrich) and titanium isopropoxide (Ti [OCH (CH ₃ ) ₂ ] ₄ ) (≥97%, Sigma -Aldrich) was added to dissolve so that the ratio of MgO to the total complex was 0.90, 0.95, 0.97 and 0.98, respectively, and then 5 ml of nitric acid (70%) was added for complete hydrolysis. After stirring for 5 hours, the solution was evaporated at 60 ° C. for 48 hours to induce self-assembly of the metal precursor. After evaporation of the solvent, the obtained solid was calcined at 5 ° C. for 5 hours at 550 ° C. to obtain MgO-TiO ₂ complex (MT _(x) , where x is the weight ratio of MgO ₎ , which is an ordered medium-sized porous adsorbent. It was.

Preparation Example 2 EM-MgO-TiO ₂  Preparation of Adsorbent

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

30 wt% of the eutectic mixture powder was physically mixed with 70 wt% of the MgO-TiO ₂ composite, and then calcined at 400 ° C. for 4 hours, thereby adsorbing (K, Li) NO ₃ enhanced MgO-TiO ₂ composite adsorbent (EM _{(0.3 )} MT _(x) ) was prepared.

Preparation Example 3 Preparation of EM-MgO

MgO obtained by firing magnesium nitrate hexahydrate at 400 ° C. for 4 hours was combined with the eutectic mixture by the method described in Preparation Example 2 to prepare a (K, Li) NO ₃ enhanced MgO adsorbent (EM-MgO).

Example 1: X-ray Diffraction Pattern (XRD) Analysis

X-ray diffraction pattern analysis (2θ = 20-80) was performed on the MT _(x) and EM _(0.3) MT _(x) adsorbents using an X-ray diffraction pattern analyzer (D-Max2500-PC, Rigaku). One result is shown in FIG. 1 (a) and FIG. 1 (b), respectively.

In the XRD pattern of FIG. 1 (a), a diffraction peak corresponding to MgO was observed, but no diffraction peak was observed due to the relatively small content of TiO ₂ . This is interpreted to be due to the TiO ₂ was evenly dispersed in the MgO frame (framework).

On the other hand, the intensity of the diffraction peak of MgO increased with the content of MgO, which means the formation of MgO crystals.

In the XRD pattern of FIG. 1B, in addition to the diffraction pattern of MgO, diffraction peaks corresponding to LiNO ₃ and KNO ₃ are present. In this case, it can be seen that the intensity of the MgO peak was reduced compared to the intensity identified in FIG. 1 (a), which means that all active species were evenly distributed throughout the sample.

Example 2: Surface Characterization

The effect of TiO ₂ incorporated into the MgO framework and the structural properties in the MT _(x) samples were investigated using N ₂ adsorption-desorption analysis.

N ₂ adsorption-desorption isotherms and pore size distributions (PSDs) measured using BELSORP-mini (BEL JAPAN INC.) At 298K for MT _(x) and EM _(0.3) MT _(x) adsorbents. 2 (a) and (b).

All samples showed IV-type adsorption isotherms and H1-type hysteresis loops from which it can be seen that the samples have mesoporous structures and cylindrical pores. Typically, N ₂ adsorption occurred at higher partial pressures (p / p ₀ > 0.5) due to the presence of medium-sized pores with larger volumes.

In the PSD graph, it can be seen that the pore size distribution of the MgO adsorbent shifted to a larger size after binding of EM, indicating that the active species forming the complex structure were redistributed.

The tissue properties of the MT _(x) and EM _(0.3) MT _(x) adsorbents were also analyzed for average crystal size, specific surface area, CO ₂ capture and MgO conversion and the results are shown in Table 1 below. CO ₂ capture and MgO conversion values were obtained from the results of Example 3 below.

In Table 1, the average crystal size was calculated from the XRD results using Scherrer's equation, the specific surface area was calculated by the BET analysis method, and CO ₂ capture was obtained by TGA analysis.

From Table 1, it can be seen that the specific surface area is greatly reduced while the MgO adsorbent binds with EM. This means that EM is better dispersed on the outer surface of the MT _(x) complex.

Example 3: CO ₂  Adsorption Performance Analysis

CO ₂ adsorption-desorption experiments were performed on both physical adsorption and chemisorbed CO ₂ using a thermogravimetric analyzer (SCINCO, TGA N-1000).

20 mg of the adsorbents prepared in Examples 1 and 2 were placed in a platinum pan and pretreated by flowing N ₂ at 100 ml / min at 400 ° C. for 60 minutes. After cooling to adsorption temperature (25 ° C.), pure CO ₂ was introduced at a flow rate of 100 ml / min. The weight change with adsorption was calculated in mmol / g. The obtained result is shown in FIG.

3 shows the CO ₂ capture performance of EM _(0.3) MT _(x) samples with different MgO content.

Since CO ₂ adsorption is directly related to the formation of MgCO ₃ by the reaction of MgO and CO ₂ , the adsorption capacity increased with MgO content.

Also noteworthy that the starting temperature (temperature at which CO ₂ adsorption starts, about 190 ° C.) and offset temperature (temperature at which CO ₂ adsorption is saturated, about 450 ° C.) were the same for all samples. This means that the properties of basicity resulting from ionization of MgO in EM are similar in all samples regardless of the dissolved content of MgO. However, the amount of basicity depends on the content of ionizable MgO.

In Table 1, the EM _(0.3) MT _(0.98) sample exhibited the highest adsorption capacity corresponding to 41.1 wt% and the highest MgO conversion corresponding to about 59%.

Example 4 CO According to Temperature ₂  Adsorption Performance Analysis

To analyze the CO2 adsorption performance of EM-MT adsorbent according to the temperature, the temperature in a dry condition from 100% CO ₂ at 250, 300, 325, 350 and 370 ℃ were analyzed for CO ₂ absorption in each case (Fig. 4 (a)).

In addition, CO ₂ adsorption was analyzed at a temperature in the range of 200 to 300 ° C. under 15% CO ₂ conditions (FIG. 4 (b)).

As can be seen in Figure 4, the CO ₂ capture initially increased as the temperature increased from 250 to 300 ° C. The maximum CO ₂ capture was observed at 300 ° C. and above 30 wt%.

However, further increase in temperature resulted in a decrease in CO ₂ capture. Interestingly, at temperatures above 300 ° C., significant CO ₂ capture was only observed at 325 ° C., corresponding to about 23% by weight. With further increase in temperature, CO ₂ capture decreased significantly.

Although these actions are seen as unfavorable, but the high temperature CO ₂ adsorption, sudden reduction of CO ₂ capture is advantageous in that it can be set precisely offset temperature for efficient reproduction of MgCO _3.

The rate of CO ₂ capture appeared very fast at low temperatures (250 ° C.) very early (<10 minutes) and reached equilibrium at 120 minutes. However, the adsorption rate decreased when the temperature was further increased. The initial 10 min CO ₂ capture curve at 300 ° C. showed a gentle increase and then quickly converted to very fast CO ₂ capture. The adsorption amount of CO ₂ at 300 ° C. was higher than that at 250 ° C., although the initial adsorption rate was slow.

The same tendency was observed for diluted CO ₂ concentrations (FIG. 4 (b)). However, the optimum temperature varied as compared to in a 100% CO ₂ atmosphere. The maximum adsorption amount was 18% by weight at 250 ° C. This means that the optimum CO ₂ adsorption temperature depends on the CO ₂ concentration.

This behavior is due to the nature / strength of the base points. Under dilute CO ₂ atmosphere, CO ₂ adsorption at 300 ° C. was significantly reduced compared to 100% CO ₂ at 2% by weight.

However, at dilute conditions, the CO ₂ adsorption was found to be higher than the known amount of CO ₂ adsorption. This means that the adsorbents of the present invention can be well adapted to CO ₂ adsorption in diluted conditions.

Example 5: Cycle Characterization

5 (a)-(c) show the cycle characteristics of EM-MgO, EM _(0.3) MT _(0.98) and EM _(0.3) MT _(0.95) adsorbents, respectively.

In FIG. 5 (a), the EM-MgO adsorbent showed good CO ₂ adsorption performance (> 35 wt%) by highly ionized MgO species. However, cycle performance decreased significantly as the number of cycles was repeated. It is believed that this is because highly active MgO species rapidly structurally relocate from cubic MgO to trigonal MgO. Although CO ₂ desorption can be promoted by dissolution of both Mg ²⁺ and CO ₃ ^2- ions at high temperatures, it is believed that the lattice deformation during the adsorption-desorption process is fast.

Figure 5 (b) shows the cycle performance of EM _(0.3) MT _(0.98) containing 2% by weight of TiO ₂ in the MgO framework. Due to the composite structure, the CO ₂ adsorption performance showed 25-35% by weight, slightly lower than 35% by weight of EM-MgO, at a similar optimum temperature of 350 ° C. At the same time, the cycle performance was continuously reduced by the following cycles.

On the other hand, in FIG. 5 (c), EM _(0.3) MT _(0.95) showed very improved cycle performance compared to EM-MgO and EMMT _(0.98) . This is considered to be because the complex structure that can control the degree of ionization of MgO minimized the structural rearrangement. In addition, the optimum adsorption temperature with higher adsorption performance was lower than that of EM-MgO samples at 300 ° C.

In FIG. 5C, the desorption temperature was 450 ° C., lower than EM-MgO and EM _(0.3) -MT _(0.98) . This narrowed temperature window has many advantages, which can be applied to a wider area because of the lower energy requirements for desorption. Allowing MgO to desorb at low temperatures can overcome the possibility of aggregation and prevent the adsorbent from losing activity.

The properties of the adsorption-desorption curves were also different from EM-MgO and EMMT _(0.98) . In the case of EM-MgO and EMMT _(0.98) , cycle performance began to decrease immediately from the second cycle. However, for the first (3) cycles of EM _(0.3) MT _(0.95) the CO ₂ capture was found to rather increase and then slowly decline.

This is believed to be due to the activation of the MgO complex. As expected, in the latter case the rate of decay was found to be reduced. EM _(0.3) MT _(0.95) adsorbent was maintained over 80% active for the first five cycles.

Example 6: Analysis of Morphology Change of Adsorbent

In order to confirm the structural changes of the adsorbent during the adsorption-desorption step, field emission scanning electron microscopy (FE-SEM) and FE-TEM investigations were carried out before the CO ₂ adsorption of EM _(0.3) MT _(0.95) and after 11 cycles. It was.

6 (a)-(f) show FE-SEM images of EM _(0.3) MT _(0.95) adsorbents before CO ₂ adsorption and after 11 cycles.

6 (a)-(c) show that the EM _(0.3) MT _(0.95) adsorbent consists of a rough surface with small particles prior to CO ₂ adsorption.

However, in Figs. 6 (d) to (f), after 11 cycles, evolution into large particles with a smooth surface was observed. This is due to the rearrangement of the molten MgO in the EM during the adsorption-desorption step.

Referring to FIG. 6 (f), which is the largest enlargement, the bulk of EM-MT (0.95) is still composed of particles of smaller size, and only the particles exposed to the outside can be confirmed that aggregation occurs due to desorption by temperature change.

7 (a)-(f) show FE-TEM images of EM _(0.3) MT _(0.95) adsorbents before CO ₂ adsorption and after 11 cycles.

The TEM image shows a change similar to the SEM image before and after 11 cycles of CO ₂ adsorption-desorption. Selected area electron diffraction (SAED) pattern means a decrease in crystallinity as a result of the formation of amorphous MgO with reduced lattice constant. This allows MgO to dissolve in the molten EM during the adsorption-desorption step.

Although EM _(0.3) MT _(0.95) adsorbents do not exhibit the highest levels of CO ₂ adsorption capacity, they are practical support groups as solid adsorbents for fluidized-bed CO ₂ capture that require strong resistance to aggregation. I believe this can be.

From the above description, those skilled in the art will appreciate that the present invention can be implemented in other specific forms without changing the technical spirit or essential features. In this regard, the embodiments described above are to be understood in all respects as illustrative and not restrictive. The scope of the present invention should be construed that all changes or modifications derived from the meaning and scope of the following claims and equivalent concepts rather than the detailed description are included in the scope of the present invention.

Claims (22)

Enhancers, including eutectic mixtures, and
Magnesium Oxide / Titanium Oxide Complex
As an adsorbent for collecting carbon dioxide,
The eutectic mixture is a eutectic mixture of potassium nitrate (KNO ₃ ) and lithium nitrate (LiNO ₃ ),
The eutectic mixture is contained 20 to 40% by weight based on the total weight of the adsorbent,
The magnesium oxide / titanium oxide composite is characterized in that the TiO ₂ 2 to 10% by weight, carbon dioxide capture adsorbent.
delete delete The method of claim 1,
The potassium nitrate and lithium nitrate are mixed in a molar ratio of 1: 1 to 1: 4, adsorbent for carbon dioxide capture.
delete delete Mixing and grinding two or more alkali nitrates to produce a eutectic mixture;
Homogenizing the eutectic mixture by heating above the eutectic temperature;
Cooling and regrinding the homogenized eutectic mixture to prepare a eutectic mixture powder;
Mixing the eutectic mixture powder with the magnesium oxide / titanium oxide complex; And
Firing the magnesium oxide / titanium oxide composite mixed with the eutectic mixture powder
As a method for producing a carbon dioxide capture adsorbent,
The eutectic mixture is a eutectic mixture of potassium nitrate and lithium nitrate,
The eutectic mixture is contained 20 to 40% by weight based on the total weight of the adsorbent,
The magnesium oxide / titanium oxide composite is characterized in that it comprises 2 to 10% by weight of TiO ₂ , method for producing a carbon dioxide capture adsorbent.
The method of claim 7, wherein
The magnesium oxide / titanium oxide complex
Adding and stirring a metal precursor and an acid including a magnesium precursor and a titanium precursor to the solvent;
Evaporating the solvent to obtain a solid; And
Calcining the solid to obtain a magnesium oxide / titanium oxide composite
Method for producing a carbon dioxide capture adsorbent, characterized in that it is prepared from.
delete The method of claim 7, wherein
The homogenization step is characterized in that carried out by heating for 8 to 16 hours at a temperature 80 to 150 ℃ higher than the eutectic temperature of the eutectic mixture, carbon dioxide capture adsorbent manufacturing method.
The method of claim 7, wherein
The firing is carried out for 4 to 8 hours at 300 to 500 ℃ under nitrogen gas, the method of producing an adsorbent for carbon dioxide capture.
The method of claim 8,
The magnesium precursor is selected from magnesium hydroxide, magnesium nitrate and magnesium acetate, method of producing an adsorbent for carbon dioxide capture.
The method of claim 8,
The titanium precursor is selected from titanium tetrabutoxide, titanium propoxide, titanium isopropoxide, titanium methoxide, and titanium ethoxide. Method for producing a carbon dioxide capture adsorbent, characterized in that.
The method of claim 8,
The firing is carried out at 500 to 900 ℃ for 4 to 10 hours, characterized in that for producing a carbon dioxide capture adsorbent.
The method of claim 8,
The acid is selected from nitric acid, acetic acid, hydrochloric acid, sulfuric acid, and combinations thereof.
The method of claim 8,
The solvent is selected from ethanol, methanol, isopropyl alcohol, and combinations thereof.
delete Inducing melting of the eutectic mixture by heating the adjuvant including the eutectic mixture and the adsorbent for capturing carbon dioxide including the magnesium oxide / titanium oxide complex above the eutectic temperature of the eutectic mixture; And
Introducing carbon dioxide gas into the adsorbent melted eutectic mixture
As a carbon dioxide adsorption method comprising:
The eutectic mixture is a eutectic mixture of potassium nitrate and lithium nitrate,
The eutectic mixture is contained 20 to 40% by weight based on the total weight of the adsorbent,
The magnesium oxide / titanium oxide composite is characterized in that the TiO ₂ 2 to 10% by weight, carbon dioxide adsorption method.
The method of claim 18,
When introducing 100% CO ₂ , the adsorbent is heated to 250 to 325 ° C., the carbon dioxide adsorption method.
The method of claim 18,
When introducing 30% or less of CO ₂ , the adsorbent is heated to 200 to 300 ° C., wherein the carbon dioxide adsorption method.
As a regenerating method of the adsorbent for carbon dioxide capture containing an enhancer comprising a eutectic mixture and a magnesium oxide / titanium oxide complex,
The eutectic mixture is a eutectic mixture of potassium nitrate and lithium nitrate,
The eutectic mixture is contained 20 to 40% by weight based on the total weight of the adsorbent,
The magnesium oxide / titanium oxide composite includes 2-10 wt% of TiO ₂ ,
The carbon dioxide adsorption is completed, the adsorbent is heated to 400 to 550 ℃ 5 to 20 minutes, characterized in that the regeneration of the adsorbent for collecting carbon dioxide.
The method of claim 21,
Regeneration method of the adsorbent for carbon dioxide capture, characterized in that the heating is carried out under N ₂ atmosphere.

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