Preparation method of a CaBTC / silica composite aerogel and its application in desulfurization

Abstract

The present invention relates to the technical field of composite functional materials, and particularly to a preparation method of CaBTC / silica composite aerogel and its application in desulfurization, which includes the following steps: S1: Prepare 1,3,5-benzenetricarboxylic acid solution and calcium acetate solution; S2: At room temperature, successively add tetraethyl orthosilicate, organosilane modifier and dopamine into the mixed solution of ethanol and water, dropwise add hydrochloric acid to adjust the pH to 2.0 - 5.0, after hydrolysis reaction, then dropwise add ammonia water to adjust the pH to 9.0 - 10.5 to obtain silica hydrogel, and further age it; S3: After washing the aged silica hydrogel to neutrality, gradually dropwise add the 1,3,5-benzenetricarboxylic acid solution into the hydrogel, after adsorption equilibrium, then dropwise add the calcium acetate solution, carry out ultrasonic reaction for 10 min - 2 h, and after washing and freeze-drying, it is obtained. The present invention combines the sol-gel method and the in-situ growth method to first load CaBTC in the silica gel structure to prepare CaBTC / silica composite aerogel, and through the combination of CaBTC and silica aerogel, sulfur dioxide gas can be synergistically and efficiently removed.

Description

Technical Field

[0001] The present invention relates to the technical field of composite functional materials, and particularly relates to a preparation method of CaBTC / silica composite aerogel and its application in desulfurization. Background Art

[0002] With the development of the industrialization process, a large amount of fossil fuels such as coal and oil are mined and used. During the combustion of fossil fuels, a large amount of SO x is emitted, causing serious environmental pollution. Sulfur dioxide is one of the main air pollutants. It will form acid rain after combining with rainwater in the high altitude. Therefore, developing efficient desulfurization materials to reduce its emission has become an urgent need in the field of environmental protection.

[0003] Silica aerogel is a lightweight and porous inorganic non-metallic material. Its structure is composed of a three-dimensional network, with a relatively high porosity (80% - 99.8%), pore size in the range of 1 - 100 nm, and has a rich microporous and mesoporous structure. These structural characteristics endow silica aerogel with a series of excellent physical properties, including low density, extremely large specific surface area, low thermal conductivity, etc., making silica aerogel widely used in the fields of thermal insulation, sound insulation, noise reduction, adsorption, etc. Although there are rich pore structures inside silica aerogel, the pure silica surface has no active groups, and its adsorption and desorption ability for sulfur dioxide gas is limited, which restricts its application in the field of sulfur dioxide capture. At present, how to improve the adsorption ability of silica aerogel porous materials for sulfur dioxide gas and give full play to the structural advantages of silica aerogel has become one of the hot issues in the field of desulfurization materials. For example, the invention patent with the application number CN202210458940.X discloses a 2D sheet structure silica-based desulfurization catalyst and its preparation method. Using the 2D sheet structure silica as a carrier, grafting a compound containing an amino group on the 2D sheet structure silica to obtain amino-modified 2D sheet structure silica, and then using heteropolyacid as the catalyst active component, anchoring the heteropolyacid molecules on the surface of the amino-modified 2D sheet structure silica to prepare a heteropolyacid-supported amino-modified 2D sheet structure silica catalyst, whose desulfurization rate reaches more than 67.9% in 30 min; for example, the invention patent with the application number CN202410535956.5 discloses a solid desulfurizer and its preparation method, using a modified porous silica / alumina carrier to chelate Zn and Fe ions, and the desulfurization rate of the prepared desulfurizer reaches more than 99.8%.

[0004] CaBTC is a typical Ca-MOFs material, which has the characteristics of good stability, low toxicity, low price, relatively low density and good biocompatibility. Ca-MOFs has potential application value in the fields of gas adsorption, separation, drug delivery, electronics, magnetism and biomedicine. Due to the sulfur-fixing ability of calcium-based materials and the good binding ability between MOFs materials and silica aerogel, the composite material obtained by in-situ composite of CaBTC in silica aerogel helps to improve the desulfurization effect of silica aerogel. Summary of the Invention

[0005] In view of this, the purpose of the present invention is to propose a preparation method of CaBTC / silica composite aerogel and its application in chemical adsorption desulfurization. On the one hand, a new composite material CaBTC / SiO 2 composite aerogel is synthesized. On the other hand, the combination of CaBTC and silica is used to improve the selective adsorption of SO 2 by silica aerogel.

[0006] Based on the above purpose, the present invention provides a preparation method of CaBTC / silica composite aerogel, which includes the following steps:

[0007] S1: Dissolve a certain amount of 1,3,5-benzenetricarboxylic acid in a mixed solution of ethanol and N,N-dimethylformamide, and ultrasonically dissolve it to obtain a 1,3,5-benzenetricarboxylic acid solution;

[0008] Dissolve calcium acetate monohydrate in deionized water and ultrasonically dissolve it to obtain a calcium acetate solution;

[0009] S2: At room temperature, add tetraethyl orthosilicate, organosilane modifier and dopamine to a mixed solution of ethanol and water in sequence, dropwise add hydrochloric acid to adjust the pH to 2.0 - 5.0, after hydrolysis reaction for a period of time, then dropwise add ammonia water to adjust the pH to 9.0 - 10.5 to obtain silica hydrogel, and further age it at a certain temperature;

[0010] By introducing an organosilane coupling agent, its different functional groups can adjust the surface hydrophilicity and hydrophobicity of the aerogel, and the hydrophilic silica aerogel can be transformed into a hydrophobic structure;

[0011] S3: After washing the aged silica hydrogel to neutral, gradually drop the 1,3,5-benzenetricarboxylic acid solution into the hydrogel. After adsorption equilibrium, then dropwise add the calcium acetate solution, and ultrasonically react for 10 min - 2 h. The obtained solid is washed and freeze-dried to obtain CaBTC / silica composite aerogel;

[0012] By dispersing calcium ions and the organic ligand 1,3,5-benzenetricarboxylic acid in a silica hydrogel and under the action of ultrasonic waves, the molecular self-assembly reaction can be quickly achieved, and a CaBTC crystal structure can be formed in the silica gel network.

[0013] Preferably, in step S1, the dosage ratio of 1,3,5-benzenetricarboxylic acid, ethanol, N,N-dimethylformamide, calcium acetate monohydrate, and deionized water is 1.0 - 2.0 mmol: 4.0 - 6.0 mL: 3.0 - 6.0 mL: 1.0 - 2.5 mmol: 4.0 - 8.0 mL.

[0014] Preferably, in steps S2 - S3, the dosage ratio of tetraethyl orthosilicate, organosilane modifier, dopamine, ethanol, water, calcium acetate solution, and 1,3,5-benzenetricarboxylic acid solution is 0.7 - 1.5 mL: 0.05 - 0.25 mL: 0.3 - 0.5 g: 10 - 20 mL: 20 mL: 2 - 3.5 mL: 2 - 3.5 mL.

[0015] Preferably, in step S2, the organosilane modifier is one or more of methyltrimethoxysilane, vinyltriethoxysilane, dimethyldiethoxysilane, ethynyltrimethoxysilane, and octadecyltrimethoxysilane.

[0016] Preferably, in step S2, the hydrolysis reaction time is 30 - 50 min.

[0017] Preferably, in step S2, the aging temperature is 35 - 60 °C and the aging time is 1 - 2 d.

[0018] Preferably, in step S3, the freeze-drying time is 1 - 3 d.

[0019] The present invention further provides the application of the CaBTC / silica composite aerogel prepared by the described preparation method in desulfurization.

[0020] The beneficial effects of the present invention:

[0021] The present invention combines the sol-gel method and the in-situ growth method to first load CaBTC in the silica gel structure to prepare a CaBTC / silica composite aerogel. Through the combination of CaBTC and the silica aerogel, sulfur dioxide gas can be synergistically and efficiently removed, and the adsorption rate of sulfur dioxide gas can reach 96.2%. At the same time, the introduction of organosilicon can improve the hydrophobic performance of the composite aerogel, enhance its waterproof performance, inhibit the water absorption and denaturation of the composite aerogel, and extend its service life. This composite material can be applied to the treatment of flue gas, sulfur-containing waste gas, etc.

[0022] Different from traditional SiO 2Synthesis method of gel. In the present invention, dopamine is added to the hydrolysis system to form polydopamine / silica hydrogel. At the same time, the amino groups in polydopamine can form hydrogen bond interactions with the hydroxyl groups in the silica hydrogel, enabling polydopamine to penetrate through the hydrogel network structure. Further, the hydroxyl groups and amino groups distributed in the hydrogel system undergo cross-linking reactions with the organic ligand 1,3,5-benzenetricarboxylic acid, thereby realizing the organic stable composite of silica and CaBTC material, and improving the target product CaBTC / SiO 2 The structural stability of the composite aerogel improves the mechanical strength of the composite aerogel to a certain extent. At the same time, the introduction of dopamine also helps to improve the selective adsorption performance of the CaBTC / silica composite aerogel for sulfur dioxide. The reason may be that the modification of silica by polydopamine makes the gel system contain a large number of active sites. As a strong Lewis acid, sulfur dioxide interacts with the amino Lewis basic groups in the aerogel, thereby greatly improving the selective capture performance of the composite aerogel for sulfur dioxide. In addition, the hydrogen atoms in the hydroxyl groups in the aerogel can form intermolecular hydrogen bond interactions with the oxygen atoms in the sulfur dioxide molecules, which also helps to improve the selective adsorption performance of the composite aerogel for sulfur dioxide.

[0023] The inventors also introduced organosilicon into the aerogel structure to improve its hydrophobic property, enhance the waterproof performance of the composite aerogel, inhibit its water absorption and denaturation, and extend its service life. Description of the Drawings

[0024] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only those of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0025] Figure 1 SEM scanning electron micrograph of the CaBTC / silica composite aerogel prepared in Example 1 of the present invention;

[0026] Figure 2 XRD spectrum of the CaBTC / silica composite aerogel prepared in Examples 2-3;

[0027] Figure 3 Infrared spectrum of the CaBTC / silica composite aerogel prepared in Example 4;

[0028] Figure 4 Schematic diagram of the desulfurization system for the product prepared in the examples or comparative examples of the present invention to adsorb sulfur dioxide;

[0029] Figure 5The desulfurization rate curve of the product prepared in the embodiment or comparative example of the present invention.

[0030] The markings in the figure are:

[0031] Figure 2 a is the XRD pattern of the CaBTC / silica composite aerogel obtained in Example 2, Figure 2 b is the XRD pattern of the CaBTC / silica composite aerogel obtained in Example 3, Figure 2 c is the standard XRD pattern of CaBTC;

[0032] Figure 3 a is the standard infrared spectrum of CaBTC, Figure 3 b is the infrared spectrum of the CaBTC / silica composite aerogel obtained in Example 4. Detailed implementation manners

[0033] To make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below in conjunction with specific embodiments.

[0034] The present invention provides a preparation method of a CaBTC / silica composite aerogel according to an embodiment, including the following steps:

[0035] S1: Dissolve a certain amount of 1,3,5-benzenetricarboxylic acid in a mixed solution of ethanol and N,N-dimethylformamide, and ultrasonically dissolve it to obtain a 1,3,5-benzenetricarboxylic acid solution;

[0036] Dissolve calcium acetate monohydrate in deionized water, and ultrasonically dissolve it to obtain a calcium acetate solution;

[0037] The dosage ratio of the 1,3,5-benzenetricarboxylic acid, ethanol, N,N-dimethylformamide, calcium acetate monohydrate, and deionized water is 1.0-2.0 mmol: 4.0-6.0 mL: 3.0-6.0 mL: 1.0-2.5 mmol: 4.0-8.0 mL;

[0038] S2: At room temperature, add tetraethyl orthosilicate, organosilane modifier, and dopamine to the mixed solution of ethanol and water in sequence, dropwise add hydrochloric acid to adjust the pH to 2.0-5.0, after hydrolysis reaction for 30-50 min, then dropwise add ammonia water to adjust the pH to 9.0-10.5 to obtain a silica hydrogel, and further age it at 35-60 °C for 1-2 d;

[0039] The organosilane modifier is one or more of methyltrimethoxysilane, vinyltriethoxysilane, dimethyldiethoxysilane, ethynyltrimethoxysilane, octadecyltrimethoxysilane;

[0040] By introducing an organosilane coupling agent, the different functional groups it has can adjust the surface hydrophilicity and hydrophobicity of the aerogel, and the hydrophilic silica aerogel can be transformed into a hydrophobic structure;

[0041] S3: After washing the aged silica hydrogel to neutral, gradually add the 1,3,5-benzenetricarboxylic acid solution to the hydrogel. After adsorption equilibrium, add the calcium acetate solution dropwise, and react ultrasonically for 10 min - 2 h. The obtained solid is washed and freeze-dried for 1 - 2 d to obtain the CaBTC / silica composite aerogel;

[0042] The dosage ratio of the tetraethyl orthosilicate, organosilane modifier, dopamine, ethanol, water, calcium acetate solution, and 1,3,5-benzenetricarboxylic acid solution is 0.7 - 1.5 mL:0.05 - 0.25 mL:0.3 - 0.5 g:10 - 20 mL:20 mL:2 - 3.5 mL:2 - 3.5 mL;

[0043] By dispersing calcium ions and the organic ligand 1,3,5-benzenetricarboxylic acid in the silica hydrogel and then under the action of ultrasonic waves, the molecular self-assembly reaction can be quickly realized and the CaBTC crystal structure can be formed in the silica gel network.

[0044] The application of the CaBTC / silica composite aerogel prepared in this example in desulfurization.

[0045] This example combines the sol-gel method and the in-situ growth method to first load CaBTC in the silica gel structure to prepare the CaBTC / silica composite aerogel. Through the combination of CaBTC and the silica aerogel, sulfur dioxide gas can be removed synergistically and efficiently, and the adsorption rate of sulfur dioxide gas can reach 96.2%. It can be applied to the treatment of flue gas, sulfur-containing waste gas, etc.

[0046] Different from the synthesis method of traditional SiO 2 gel, in this example, dopamine is added to the hydrolysis system to form a polydopamine / silica hydrogel. At the same time, the amino group in polydopamine can form a hydrogen bond with the hydroxyl group in the silica hydrogel, so that polydopamine penetrates through the hydrogel network structure. Further, the hydroxyl group and amino group distributed in the hydrogel system react with the organic ligand 1,3,5-benzenetricarboxylic acid to crosslink, thereby realizing the organic combination of silica and CaBTC materials and improving the target product CaBTC / SiO 2The structural stability of the composite aerogel improves the mechanical strength of the composite aerogel to a certain extent. At the same time, the introduction of dopamine also helps to improve the selective adsorption performance of the CaBTC / silica composite aerogel for sulfur dioxide. The reason may be that the modification of silica by polydopamine makes the gel system contain a large number of active sites. As a strong Lewis acid, sulfur dioxide interacts with the amino Lewis basic groups in the aerogel, thereby greatly improving the selective capture performance of the composite aerogel for sulfur dioxide. In addition, the hydrogen atom in the hydroxyl group of the aerogel can form an intermolecular hydrogen bond with the oxygen atom in the sulfur dioxide molecule, which also helps to improve the selective adsorption performance of the composite aerogel for sulfur dioxide.

[0047] The inventors also introduced organosilicon into the aerogel structure to improve its hydrophobicity, enhance the waterproof performance of the composite aerogel, inhibit its water absorption and denaturation, and extend its service life.

[0048] Example 1 Preparation of CaBTC / silica composite aerogel

[0049] S1: Dissolve 1.0 mmol of 1,3,5-benzenetricarboxylic acid in a mixed solution of 4.0 mL of ethanol and 4.0 mL of N,N-dimethylformamide (DMF), and dissolve it by ultrasonic to obtain a 1,3,5-benzenetricarboxylic acid solution;

[0050] Dissolve 1.5 mmol of calcium acetate monohydrate in 4.0 mL of deionized water, and dissolve it by ultrasonic to obtain a calcium acetate solution;

[0051] S2: Dissolve 1.0 mL of tetraethyl orthosilicate, 0.35 mL of methyltrioxymethylsilane and 0.3 g of dopamine at room temperature in a mixed solution of 10 mL of ethanol and 20 mL of water, add hydrochloric acid to adjust the pH value to 2.5, and after hydrolysis reaction for 30 min, then add a certain amount of ammonia water to the system to adjust the pH value of the system to 9.0 to obtain a silica hydrogel, and further age it at 40 °C for 1 d;

[0052] S3: Wash the aged silica hydrogel with water until neutral, gradually add 2.0 mL of the 1,3,5-benzenetricarboxylic acid solution to the hydrogel, after adsorption equilibrium, then add 2.0 mL of the calcium acetate solution to this system, react ultrasonically for 30 min, wash the obtained solid alternately with ethanol and water 3 times, and freeze-dry for 1 d to obtain the CaBTC / silica composite aerogel.

[0053] Example 2 Preparation of CaBTC / silica composite aerogel

[0054] S1: Dissolve 2.0 mmol of 1,3,5-benzenetricarboxylic acid in a mixed solution of 4.0 mL of ethanol and 6 mL of N,N-dimethylformamide (DMF), and dissolve it by ultrasonic treatment to obtain a 1,3,5-benzenetricarboxylic acid solution;

[0055] Dissolve 1.5 mmol of calcium acetate monohydrate in 6 mL of deionized water, and dissolve it by ultrasonic treatment to obtain a calcium acetate solution;

[0056] S2: Dissolve 0.8 mL of tetraethyl orthosilicate, 0.35 mL of vinyltriethoxysilane, and 0.3 g of dopamine in a mixed solution of 15 mL of ethanol and 20 mL of water at room temperature. Add hydrochloric acid to adjust the pH value to 3.5. After hydrolysis reaction for 30 min, add a certain amount of ammonia water to the system to adjust the pH value of the system to 9.5 to obtain a silica hydrogel, and further age it at 35 °C for 2 d;

[0057] S3: Wash the aged silica hydrogel 3 times with water. Gradually add 2.0 mL of the 1,3,5-benzenetricarboxylic acid solution to the hydrogel. After adsorption equilibrium, add 2.0 mL of the calcium acetate solution to this system, and react ultrasonically for 40 min. Wash the obtained solid alternately with ethanol and water 3 times, and freeze-dry it for 3 d to obtain a CaBTC / silica composite aerogel.

[0058] Example 3 Preparation of CaBTC / silica composite aerogel

[0059] S1: Dissolve 1.5 mmol of 1,3,5-benzenetricarboxylic acid in a mixed solution of 6.0 mL of ethanol and 6.0 mL of N,N-dimethylformamide (DMF), and dissolve it by ultrasonic treatment to obtain a 1,3,5-benzenetricarboxylic acid solution;

[0060] Dissolve 2.0 mmol of calcium acetate monohydrate in 8.0 mL of deionized water, and dissolve it by ultrasonic treatment to obtain a calcium acetate solution;

[0061] S2: Dissolve 1.0 mL of tetraethyl orthosilicate, 0.26 mL of dimethyldiethoxysilane, and 0.4 g of dopamine in a mixed solution of 15 mL of ethanol and 20 mL of water at room temperature. Add hydrochloric acid to adjust the pH value to 3.5. After hydrolysis reaction for 30 min, add a certain amount of ammonia water to the system to adjust the pH value of the system to 9.5 to obtain a silica hydrogel, and further age it at 60 °C for 2 d;

[0062] S3: Wash the aged silica hydrogel 3 times with water. Gradually add 2.5 mL of the 1,3,5-benzenetricarboxylic acid solution to the hydrogel. After adsorption equilibrium, add 2.5 mL of the calcium acetate solution to this system, and react ultrasonically for 50 min. Wash the obtained solid alternately with ethanol and water 3 times, and freeze-dry it for 1 d to obtain a CaBTC / silica composite aerogel.

[0063] Example 4 Preparation of CaBTC / Silica Composite Aerogel

[0064] S1: Dissolve 1.5 mmol of 1,3,5-benzenetricarboxylic acid in a mixed solution of 5.0 mL of ethanol and 4.5 mL of N,N-dimethylformamide (DMF), and dissolve it by ultrasonic treatment to obtain a 1,3,5-benzenetricarboxylic acid solution;

[0065] Dissolve 2.5 mmol of calcium acetate monohydrate in 6.0 mL of deionized water, and dissolve it by ultrasonic treatment to obtain a calcium acetate solution;

[0066] S2: Dissolve 0.7 mL of tetraethyl orthosilicate, 0.3 mL of ethynyltrimethoxysilane and 0.4 g of dopamine in a mixed solution of 15 mL of ethanol and 20 mL of water at room temperature. Add hydrochloric acid to adjust the pH value to 3.5. After hydrolysis reaction for 30 min, add a certain amount of ammonia water to the system to adjust the pH value of the system to 10.0 to obtain a silica hydrogel, and further age it at 50 °C for 2 d;

[0067] S3: Wash the aged silica hydrogel 3 times with water. Gradually add 3.5 mL of the 1,3,5-benzenetricarboxylic acid solution to the hydrogel. After adsorption equilibrium, add 3.0 mL of the calcium acetate solution to the system and react ultrasonically for 45 min. Wash the obtained solid alternately with ethanol and water 3 times and freeze-dry it for 1 d to obtain the CaBTC / silica composite aerogel.

[0068] Example 5 Preparation of CaBTC / Silica Composite Aerogel

[0069] S1: Dissolve 1.0 mmol of 1,3,5-benzenetricarboxylic acid in a mixed solution of 4.5 mL of ethanol and 3.0 mL of N,N-dimethylformamide (DMF), and dissolve it by ultrasonic treatment to obtain a 1,3,5-benzenetricarboxylic acid solution;

[0070] Dissolve 1.5 mmol of calcium acetate monohydrate in 4.5 mL of deionized water, and dissolve it by ultrasonic treatment to obtain a calcium acetate solution;

[0071] S2: Dissolve 1.5 mL of tetraethyl orthosilicate, 0.45 mL of octadecyltrimethoxysilane and 0.5 g of dopamine in a mixed solution of 20 mL of ethanol and 20 mL of water at room temperature. Add hydrochloric acid to adjust the pH value to 3.0. After hydrolysis reaction for 50 min, add a certain amount of ammonia water to the system to adjust the pH value of the system to 10.0 to obtain a silica hydrogel, and further age it at 60 °C for 1 d;

[0072] S3: Wash the aged silica hydrogel three times with water. Gradually add 3.5 mL of 1,3,5-benzenetricarboxylic acid solution dropwise to the hydrogel. After adsorption equilibrium, add 3.5 mL of calcium acetate solution dropwise to the system, and react ultrasonically for 60 min. Wash the obtained solid alternately with ethanol and water three times, and freeze-dry for 2 days to obtain the CaBTC / silica composite aerogel.

[0073] Prepare CaBTC in Comparative Example 1

[0074] S1: Dissolve 1.0 mmol of 1,3,5-benzenetricarboxylic acid in a mixed solution of 4.0 mL of ethanol and 4.0 mL of N,N-dimethylformamide (DMF), and dissolve ultrasonically to obtain a 1,3,5-benzenetricarboxylic acid solution;

[0075] Dissolve 1.5 mmol of calcium acetate monohydrate in 4.0 mL of deionized water, and dissolve ultrasonically to obtain a calcium acetate solution;

[0076] S2: Rapidly add 2.0 mL of calcium acetate solution to 4.0 mL of 1,3,5-benzenetricarboxylic acid solution, react ultrasonically for 30 min to form a white precipitate, and wash alternately with ethanol and water three times to obtain CaBTC.

[0077] Prepare organosilicon-modified silica aerogel in Comparative Example 2

[0078] Dissolve 1.0 mL of tetraethyl orthosilicate and 0.35 mL of methyltrimethoxysilane at room temperature in a mixed solution of 10 mL of ethanol and 20 mL of water. Add hydrochloric acid to adjust the pH value to 2.5, and after hydrolysis reaction for 30 min, add a certain amount of ammonia water to the system to adjust the pH value of the system to 9.0 to obtain a silica hydrogel. Further age at 40 °C for 1 day, wash the aged silica hydrogel three times with water, and freeze-dry for 1 day to obtain the organosilicon-modified silica aerogel.

[0079] Prepare CaBTC / silica composite aerogel in Comparative Example 3

[0080] S1: Dissolve 1.0 mmol of 1,3,5-benzenetricarboxylic acid in a mixed solution of 4.0 mL of ethanol and 4.0 mL of N,N-dimethylformamide (DMF), and dissolve ultrasonically to obtain a 1,3,5-benzenetricarboxylic acid solution;

[0081] Dissolve 1.5 mmol of calcium acetate monohydrate in 4.0 mL of deionized water, and dissolve ultrasonically to obtain a calcium acetate solution;

[0082] S2: Dissolve 1.0 mL of tetraethyl orthosilicate and 0.35 mL of methyltrioxymethylsilane in a mixed solution of 10 mL of ethanol and 20 mL of water at room temperature. Add hydrochloric acid to adjust the pH value to 2.5. After hydrolysis for 30 min, add a certain amount of ammonia water to the system to adjust the pH value of the system to 9.0 to obtain a silica hydrogel, and further age it at 40 °C for 1 day;

[0083] S3: Wash the aged silica hydrogel three times with water. Gradually add 2.0 mL of 1,3,5-benzenetricarboxylic acid solution to the hydrogel. After adsorption equilibrium, add calcium acetate solution to this system and react ultrasonically for 30 min. The obtained solid is washed three times alternately with ethanol and water, and freeze-dried for 1 day to obtain a CaBTC / silica composite aerogel.

[0084] I. Characterize the structure and properties of the products prepared in the examples:

[0085] Figure 1 SEM scanning electron micrograph of the CaBTC / silica composite aerogel prepared in Example 1: It can be seen from the figure that the silica aerogel and CaBTC are stably combined together, and there are abundant pores in the composite aerogel, which is beneficial to the adsorption of sulfur dioxide gas.

[0086] Figure 2 XRD spectra of the CaBTC / silica composite aerogels prepared in Examples 2-3, where Figure 2 a is the XRD spectrum of the CaBTC / silica composite aerogel obtained in Example 2, Figure 2 b is the XRD spectrum of the CaBTC / silica composite aerogel obtained in Example 3, Figure 2 c is the standard XRD spectrum of CaBTC. By comparison, it can be seen that the crystal structure of CaBTC remains unchanged in the silica aerogel, indicating that CaBTC can stably exist in the silica aerogel structure.

[0087] Figure 3 Infrared spectrum of the CaBTC / silica composite aerogel prepared in Example 4, where Figure 3 a is the standard infrared spectrum of CaBTC, Figure 3 b is the infrared spectrum of the CaBTC / silica composite aerogel obtained in Example 4. From Figure 3 b, the characteristic peaks of CaBTC and silica can be observed respectively, which proves that the CaBTC / silica composite aerogel is successfully prepared in the present invention.

[0088] II. Test the performance of the products prepared in Examples 1-5 and Comparative Examples 1-3. The desulfurization efficiency detection method is as follows:

[0089] As shown Figure 4 in the figure, a mixer is used to mix SO with a volume fraction of 50% 2 and 50% N 2 . The intake air volume is controlled by a flow meter. The gas adsorption system is a vertical fixed-phase reactor. The inside of the vertical furnace is a quartz wool insulation layer, and the center is a quartz tube reactor (d = 1.0 cm, effective area is 10.0 cm). Quartz wool is inserted at the upper and lower parts of the reactor. The desulfurization adsorption material prepared in the example or comparative example is placed in the central area of the quartz tube reaction. The system is heated to 600 °C, and the mixed gas is introduced from the bottom. After passing through the chemical adsorbent for 40 min, the gas discharged from the upper port enters the gas chromatograph to detect the concentration of SO 2 , determine the desulfurization rate, and the remaining unreacted gas is treated with an alkali solution. The desulfurization rate is calculated according to formula (I):

[0090]

[0091] The structural parameters and desulfurization rates of the product samples prepared in Examples 1-5 and Comparative Examples 1-3 are compared as shown in Table 1. The specific test results are as Figure 5 shown:

[0092] Table 1

[0093]

[0094]

[0095] As can be seen from Table 1 and Figure 5 , the desulfurization rates of the CaBTC / silica composite aerogels prepared in Examples 1-5 all reach more than 80%. However, there are also significant differences in the desulfurization rates among different examples. Among them, the desulfurization rate of Example 2 is the highest, reaching 96.2%, while the desulfurization rate of Example 5 is the lowest, being 81.4%. However, the specific surface area of Example 5 is slightly higher than that of Example 2, indicating that in the present invention, the specific surface area is not the only factor affecting the desulfurization efficiency. Another key factor affecting the desulfurization efficiency is the composite dosage ratio of CaBTC and silica. Within a certain range, increasing the dosage ratio of CaBTC and silica can improve the desulfurization efficiency. Therefore, the present invention can achieve a better desulfurization effect by reasonably adjusting the specific surface area of the CaBTC / silica composite aerogel and the composite dosage ratio of CaBTC and silica.

[0096] Meanwhile, by comparing the test data of Example 1 and Comparative Example 3, it can be seen that using polydopamine-modified silica aerogel helps to improve the desulfurization rate of the composite aerogel. At the same time, the desulfurization rate of Comparative Example 3 is higher than that of Comparative Example 1 and far better than that of Comparative Example 2, indicating that the composite of CaBTC and silica aerogel can synergistically and efficiently remove sulfur dioxide gas and improve the desulfurization effect.

[0097] From the test data of Examples 1-3, it can be seen that using polydopamine-modified silica aerogel helps to improve the desulfurization rate of the composite aerogel, and CaBTC and polydopamine-modified silica aerogel can synergistically improve the desulfurization effect of the composite aerogel.

[0098] Those of ordinary skill in the art should understand that: the discussion of any above embodiment is only exemplary and is not intended to imply that the scope of the present invention (including the claims) is limited to these examples; under the concept of the present invention, the technical features in the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations in different aspects of the present invention as described above, which are not provided in detail for the sake of brevity.

[0099] The present invention is intended to cover all such substitutions, modifications, and variations that fall within the broad scope of the appended claims. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. Application of a CaBTC / silicon dioxide composite aerogel in desulfurization, characterized in that: The desulfurization rate of the composite aerogel for sulfur dioxide gas reaches 81.4-96.2%. The preparation method of the CaBTC / silicon dioxide composite aerogel comprises the following steps: S1: dissolving a certain amount of 1,3,5-benzenetricarboxylic acid in a mixed solution of ethanol and N,N-dimethylformamide, and dissolving by ultrasonication to obtain a 1,3,5-benzenetricarboxylic acid solution; Dissolve calcium acetate monohydrate in deionized water and dissolve by ultrasonication to obtain a calcium acetate solution; S2: at room temperature, tetraethyl orthosilicate, an organosilane modifier and dopamine are sequentially added to a mixed solution of ethanol and water, hydrochloric acid is added dropwise to adjust the pH to 2.0-5.0, and after a period of hydrolysis reaction, ammonia water is added dropwise to adjust the pH to 9.0-10.5 to obtain a silica hydrogel, which is further aged at a certain temperature; S3: After the aged silica hydrogel is washed with water until it is neutral, 1,3,5-benzenetricarboxylic acid solution is gradually added dropwise to the hydrogel. After adsorption equilibrium, calcium acetate solution is added dropwise and ultrasonically reacted for 10min-2h. The obtained solid is washed and freeze-dried to obtain CaBTC / silica composite aerogel.

2. The use of a CaBTC / silicon dioxide composite aerogel in desulfurization according to claim 1, characterized in that: In step S1, the usage ratio of 1,3,5-benzenetricarboxylic acid, ethanol, N,N-dimethylformamide, calcium acetate monohydrate, and deionized water is 1.0-2.0 mmol:4.0-6.0 mL:3.0-6.0 mL:1.0-2.5 mmol:4.0-8.0 mL.

3. The use of a CaBTC / silicon dioxide composite aerogel in desulfurization according to claim 1, characterized in that: In steps S2-S3, the dosage ratio of the tetraethyl orthosilicate, the organosilane modifier, dopamine, ethanol, water, the calcium acetate solution, and the 1,3,5-benzenetricarboxylic acid solution is 0.7-1.5 mL: 0.05-0.25 mL: 0.3-0.5 g: 10-20 mL: 20 mL: 2-3.5 mL: 2-3.5 mL.

4. The use of a CaBTC / silicon dioxide composite aerogel in desulfurization according to claim 3, characterized in that: In step S2, the organosilane modifier is one or more of methyltrimethoxysilane, vinyltriethoxysilane, dimethyldiethoxysilane, and octadecyltrimethoxysilane.

5. The use of a CaBTC / silicon dioxide composite aerogel in desulfurization according to claim 1, characterized in that: In step S2, the hydrolysis reaction time is 30-50 min.

6. The use of a CaBTC / silicon dioxide composite aerogel in desulfurization according to claim 1, characterized in that: In step S2, the aging temperature is 35-60°C and the aging time is 1-2 days.

7. The use of a CaBTC / silicon dioxide composite aerogel in desulfurization according to claim 1, characterized in that: In step S3, the freeze-drying time is 1-3 days.

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