Silicon dioxide aerogel loaded magnesium oxide carbon dioxide adsorbent and preparation method thereof

Abstract

The invention discloses a silicon dioxide aerogel loaded magnesium oxide carbon dioxide adsorbent and a preparation method thereof, the carbon dioxide adsorbent takes silicon dioxide aerogel as a carrier and magnesium oxide as a carbon dioxide adsorption active component, and the magnesium oxide is loaded on the surface and in an internal pore structure of the silicon dioxide aerogel. The preparation method comprises the following steps: (1) preparing silicon dioxide aerogel by a sol-gel method; (2) soaking the silicon dioxide aerogel in a magnesium salt solution; (3) reacting the silicon dioxide aerogel loaded with the magnesium salt with soluble carbonate or aqueous alkali to convert into magnesium carbonate or magnesium hydroxide; and (4) performing high-temperature calcination to obtain a final product. According to the carbon dioxide adsorbent, the high specific surface area and porous structure of the silicon dioxide aerogel are combined with the carbon dioxide adsorption performance of magnesium oxide, the problem that the specific surface area is small due to the fact that magnesium oxide is prone to agglomeration is effectively solved, and the carbon dioxide adsorbent shows excellent performance in the field of carbon dioxide adsorption.

Description

Technical Field

[0001] This invention belongs to the field of carbon dioxide adsorption, specifically relating to a carbon dioxide adsorbent supported on magnesium oxide in silica aerogel and its preparation method. Background Technology

[0002] Carbon dioxide released from industrial activities (such as thermal power generation and steel smelting) and indoor environments (such as air conditioning systems) is a major contributor to global warming. Traditional carbon dioxide treatment technologies suffer from problems such as high corrosivity, high regeneration energy consumption, and the need for frequent maintenance; therefore, adsorption methods are commonly used in the carbon dioxide field. Chinese patent CN120437948A discloses a carbon dioxide adsorbent that uses calcium hydroxide or magnesium hydroxide as the active particle shell and calcium oxide or magnesium oxide as the active particle core, achieving efficient adsorption of carbon dioxide at 300-700℃. However, traditional calcium-based adsorbents are prone to sintering, agglomeration, and structural collapse after repeated high-temperature adsorption and desorption cycles, leading to a decline in adsorption performance and stability.

[0003] Magnesium oxide (MgO) is an inorganic oxide with stable chemical properties, is non-toxic and harmless, and is widely available with a simple synthesis process, meeting the requirements of green chemistry. The reaction of MgO with carbon dioxide is a chemical adsorption process to form magnesium carbonate. This chemical adsorption exhibits strong binding force and high selectivity for carbon dioxide, effectively adsorbing even in low-concentration carbon dioxide environments, with minimal interference from other gases (such as nitrogen and oxygen). The optimal adsorption temperature range for MgO is 400–700℃, allowing direct application to carbon dioxide capture in high-temperature industrial waste gases without additional cooling, thus reducing energy consumption. Compared to low-temperature adsorbents (such as activated carbon, suitable for below room temperature), it can adapt to the high-temperature characteristics of industrial exhaust gases, avoiding energy loss due to cooling. MgO can be improved by loading it onto porous supports (such as silica aerogel and activated carbon) or by doping it with metal oxides, thereby enhancing its specific surface area, pore structure, and anti-sintering ability, improving adsorption rate and cycle life. Chinese patent CN103894152A discloses a medium- and high-temperature carbon dioxide adsorbent and its preparation method. The carbon dioxide adsorbent uses magnesium oxide as the active ingredient and alumina as a porous carrier, and can efficiently adsorb carbon dioxide at temperatures of 200-400℃ and in high-temperature environments.

[0004] Magnesium oxide has significant drawbacks as a carbon dioxide adsorbent, with low utilization of its active sites leading to low adsorption efficiency. Therefore, a high-efficiency carrier is urgently needed to improve its performance. This invention aims to provide a silica aerogel-supported magnesium oxide carbon dioxide adsorbent and its preparation method, thereby addressing the aforementioned problems. Summary of the Invention

[0005] The present invention aims to provide a silica aerogel-supported magnesium oxide carbon dioxide adsorbent and its preparation method. This carbon dioxide adsorbent uses magnesium oxide as the active carbon dioxide adsorption component. Magnesium oxide is loaded onto the pores and surface of a silica aerogel with a specific surface area of ​​100-1000 m² / g and a median pore size between 2-50 nm, forming a highly efficient carbon dioxide adsorbent. Silica aerogel is prepared using orthosilicate as the silicon source via a solution gelation method. Magnesium ions are adsorbed onto the silica aerogel using an impregnation method, and then added to a soluble carbonate solution to obtain silica aerogel-supported magnesium carbonate. High-temperature calcination yields a silica aerogel-supported magnesium oxide carbon dioxide adsorbent with high carbon dioxide adsorption performance.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: a method for preparing a carbon dioxide adsorbent supported on magnesium oxide in silica aerogel, comprising the following steps:

[0007] A method for preparing a silica aerogel-supported magnesium oxide carbon dioxide adsorbent includes the following steps:

[0008] (1) Preparation of silica aerogel: Tetraethyl orthosilicate, ethanol, and water were mixed in a certain proportion, and the pH was adjusted to 2-3 with hydrochloric acid and reacted for 4 hours. Ammonia was added to adjust the pH to 7-8 to form a gel. After aging, the gel was immersed in a mixture of the modifier trithiotrimethylsilane (TEOS) and n-hexane, stirred, precipitated, and the supernatant was removed. The silica aerogel was obtained by drying at room temperature.

[0009] (2) Loading soluble magnesium salts: Mix magnesium chloride solution, magnesium sulfate or magnesium nitrate with silica aerogel, stir at a certain temperature for a period of time, and filter to obtain silica aerogel loaded with magnesium salts.

[0010] (3) Conversion to magnesium carbonate: Add magnesium salt-loaded silica aerogel to sodium carbonate solution and stir. After filtration, washing with water and drying, magnesium carbonate-loaded silica aerogel is obtained.

[0011] (4) Preparation of carbon dioxide adsorbent by calcination: Calcination of silica aerogel loaded with magnesium carbonate at high temperature under nitrogen atmosphere to obtain carbon dioxide adsorbent loaded with magnesium oxide in silica aerogel.

[0012] Preferably, the molar ratio of tetraethyl orthosilicate, ethanol and water in step (1) is 1:(3-5):(6-10).

[0013] Preferably, the modifier in step (1) is a mixture of trithiotrimethylsilane and n-hexane in a volume ratio of 1:2 to 1:6.

[0014] Preferably, in step (2), the concentration of magnesium chloride, magnesium sulfate, or magnesium nitrate solution is 10 g / L to 90 g / L, the stirring temperature is 60 °C, and the time is 2 h.

[0015] Preferably, the soluble carbonate in step (3) is sodium carbonate, with a solution concentration of 10 g / L, and is stirred at room temperature for 30 min.

[0016] Preferably, the calcination temperature in step (4) is 500-700℃ and the time is 0.5 to 4h.

[0017] The beneficial effects of this invention are:

[0018] (1) A silica aerogel was prepared by a simple and safe sol-gel method and atmospheric pressure drying method, and then combined with magnesium oxide to successfully prepare a carbon dioxide adsorbent with high reactivity of silica aerogel loaded with magnesium oxide.

[0019] (2) Silica aerogel, as a carrier, has an ultra-high specific surface area (100-1000 m² / g) and contains interpenetrating channels of 2-50 nm. It has advantages such as low density, good chemical stability and surface modifiability. It can effectively disperse and fix magnesium oxide nanoparticles, inhibit their aggregation and improve their adsorption performance.

[0020] (3) The carbon dioxide adsorbent prepared by the present invention has the adsorption performance of magnesium oxide and the high dispersibility and high adsorption characteristics of aerogel, and presents unique advantages in the field of carbon dioxide conversion.

[0021] (4) Experimental results show that the carbon dioxide adsorbent exhibits excellent performance when adsorbing carbon dioxide, opening up new application space for aerogel materials as adsorbent carriers. Attached Figure Description

[0022] Figure 1 This is a graph showing the specific surface area (BET) of silica aerogel.

[0023] Figure 2 This is a scanning electron microscope (SEM) image of silica aerogel.

[0024] Figure 3 This is a scanning electron microscope (SEM) image of magnesium oxide supported on silica aerogel.

[0025] Figure 4 X-ray diffraction (XRD) patterns of silica aerogel and silica aerogel loaded with magnesium oxide.

[0026] Figure 5 Carbon dioxide adsorption curves for magnesium oxide and magnesium oxide supported on silica aerogel. Detailed Implementation

[0027] The technical solutions of the present invention will be described in detail below with reference to the embodiments of the present invention. The described embodiments are merely some embodiments of the present invention and are used to explain the present invention, not to limit the present invention.

[0028] Example 1

[0029] The method for preparing silica aerogel-supported magnesium oxide carbon dioxide adsorbent is as follows: TEOS, ethanol, and water are added to a container in a molar ratio of 1:4:8, and the mixture is stirred until homogeneous. The pH of the system is adjusted to 2-3 with 1 mol / L hydrochloric acid solution, and the reaction is carried out for 4 hours. Subsequently, 1 mol / L ammonia solution is added to adjust the pH to 7.6, and a white transparent gel is formed. The gel is aged at 45℃ for 24 hours. After aging, it is crushed and immersed in 100 mL of a mixed solution prepared from trithiotrimethylsilane and n-hexane in a volume ratio of 1:3.5. The solution is magnetically stirred at 40℃ for 5 hours, allowed to stand for 1 hour to precipitate, and then the supernatant is discarded. The modified gel is dried at room temperature for 12 hours, and then dried at 150℃ for 3 hours to obtain silica aerogel. Figure 1 The graph shows the specific surface area (BET) of silica aerogel. Figure 1 It can be seen that the specific surface area of ​​the silica aerogel is 683 m². 2 / g, with a micropore ratio as high as 68% and an average pore size of 2.13nm. Figure 2 This is a scanning electron microscope (SEM) image of silica aerogel.

[0030] Prepare 50 mL of magnesium chloride solution with a concentration of 50 g / L, add 0.5 g of silica aerogel, stir at 60 °C for 2 h, filter using a microporous membrane, and dry the filter residue to obtain magnesium chloride-loaded silica aerogel.

[0031] Magnesium chloride-loaded silica aerogel was added to a 10 g / L Na2CO3 solution and stirred at room temperature for 30 min. After filtration and washing with water 3-4 times, the aerogel was dried and then washed with water 3-4 times and dried again to obtain magnesium carbonate-loaded silica aerogel. The aerogel was then calcined at 600 °C for 1 h under a nitrogen atmosphere to obtain magnesium oxide-loaded silica aerogel. Figure 3 This is a scanning electron microscope (SEM) image of magnesium oxide supported on silica aerogel. Figure 4 X-ray diffraction (XRD) patterns of silica aerogel and magnesium oxide supported on silica aerogel are shown below. Figure 4 It can be seen that the silica aerogel supporting magnesium oxide is an amorphous system with no characteristic diffraction peaks. The XRD patterns before and after magnesium oxide loading remain basically unchanged, indicating that no new crystal form has formed in the system.

[0032] Carbon dioxide adsorption experiments were conducted on a sample of magnesium oxide-supported silica aerogel as a carbon dioxide adsorbent. The silica aerogel-supported magnesium oxide sample and the magnesium oxide sample were vacuum-dried at 120℃ for 6 hours in a vacuum drying oven. First, 15 mg of the silica aerogel-supported magnesium oxide sample was weighed and spread evenly in a crucible, which was then placed in a thermogravimetric analyzer. A specific temperature control program was set: the temperature was increased from room temperature to 500℃ at a rate of 10℃ / min, then held at that temperature for 30 minutes, and then the temperature was reduced from 500℃ to 200℃ under N2 atmosphere. When the temperature dropped to 200℃, the gas atmosphere was switched to carbon dioxide and held at that temperature for 1 hour, then switched back to N2 and the temperature was increased again. These steps allowed the determination of the single-pass carbon dioxide adsorption capacity of the prepared sample. The testing method for magnesium oxide powder samples was similar.

[0033] Figure 5 Carbon dioxide adsorption curves for magnesium oxide powder and magnesium oxide supported on silica aerogel. From Figure 5 It can be seen that the adsorption capacity of magnesium oxide carbon dioxide adsorbent supported on silica aerogel reaches 0.89 mmol / g, which is significantly higher than that of pure magnesium oxide (0.48 mmol / g), indicating that the adsorption effect of carbon dioxide is significantly improved after silica aerogel is supported on magnesium oxide.

[0034] The above description is merely an embodiment of the present invention and is not intended to limit the present invention in any way. Any person skilled in the art can make some modifications or alterations to the methods and techniques disclosed above without departing from the scope of the present invention to create equivalent embodiments. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A carbon dioxide adsorbent supported on magnesium oxide in silica aerogel, characterized in that, The carbon dioxide adsorbent is composed of silica aerogel as a carrier and magnesium oxide as the active component of the carbon dioxide adsorbent, wherein the magnesium oxide is loaded on the surface and in the pore structure of the silica aerogel.

2. The carbon dioxide adsorbent according to claim 1, characterized in that, The specific surface area of ​​the silica aerogel is 100-1000 m² / g.

3. The carbon dioxide adsorbent according to claim 1, characterized in that, The median pore size distribution of the silica aerogel is between 2 and 50 nm.

4. The application of the carbon dioxide adsorbent according to any one of claims 1-3 in the industrial adsorption of carbon dioxide.

5. A method for preparing a carbon dioxide adsorbent of silica aerogel supported on magnesium oxide as described in any one of claims 1-3, characterized in that, Includes the following steps: (1) Preparation of silica aerogel: Tetraethyl orthosilicate, ethanol and water are mixed, the pH is adjusted to 2-3 with hydrochloric acid and reacted for 4 hours. Ammonia water is added to adjust the pH to 7-8 to generate a gel. After aging the gel, it is immersed in a modifier, stirred, precipitated, and the upper liquid is removed. The silica aerogel is then dried at room temperature. (2) Magnesium salt loaded: magnesium chloride, magnesium sulfate or magnesium nitrate solution is mixed with silica aerogel, stirred at a certain temperature, and filtered to obtain magnesium salt loaded silica aerogel. (3) Conversion to magnesium carbonate: Add magnesium salt-loaded silica aerogel to sodium carbonate solution and stir. After filtration, washing with water and drying, magnesium carbonate-loaded silica aerogel is obtained. (4) Preparation of catalyst by calcination: Calcination of silica aerogel loaded with magnesium carbonate at high temperature under nitrogen atmosphere to obtain carbon dioxide adsorbent loaded with magnesium oxide in silica aerogel.

6. The preparation method according to claim 5, characterized in that, In step (1), the molar ratio of tetraethyl orthosilicate, ethanol and water is 1:(3-5):(6-10).

7. The preparation method according to claim 5, characterized in that, In step (1), the modifier is a mixture of trithiotrimethylsilane and n-hexane in a volume ratio of 1:2 to 1:

6.

8. The preparation method according to claim 6, characterized in that, In step (2), the concentration of magnesium chloride, magnesium sulfate, or magnesium nitrate solution is 10 g / L to 90 g / L, the stirring temperature is 60 °C, and the time is 2 h.

9. The preparation method according to claim 6, characterized in that, In step (4), the calcination temperature is 500-700℃ and the time is 0.5 to 4 hours.

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