Preparation method of GQDs-doped molecular sieve for efficiently adsorbing carbon dioxide

Abstract

The invention provides a preparation method of a GQDs doped molecular sieve for efficiently adsorbing carbon dioxide, which is characterized by comprising the following steps: S1, mixing and dissolving aluminum chloride, sodium silicate and potassium silicate in deionized water, and stirring to obtain a precursor solution; s2, performing ultrasonic treatment on the dissolved precursor solution; s3, adding N-GQDs into the precursor solution, performing stirring treatment again, and then performing hydrothermal reaction in a reaction kettle; and S4, centrifuging, washing, drying and grinding the solution after the reaction is completed to obtain the GQD doped molecular sieve. The method has the effect of improving the carbon dioxide adsorption capacity of the molecular sieve.

Description

Technical Field

[0001] This invention relates to the technical field of porous materials, and in particular to a method for preparing GQDs-doped molecular sieves that efficiently adsorb carbon dioxide. Background Art

[0002] Carbon dioxide is one of the major greenhouse gases, and its continuously increasing concentration in the atmosphere is a major cause of global warming. Reducing CO2 emissions, especially capturing CO2 from large point sources (such as coal / gas-fired power plants, steel mills, cement plants, and chemical plants), is key to mitigating climate change. Molecular sieves, as highly efficient solid adsorbents, are one of the core materials in carbon capture and storage (CFS) technology. Through adsorption, CO2 can be separated and concentrated from industrial flue gas, facilitating subsequent transportation, utilization, or safe geological storage, thereby significantly reducing the amount of CO2 entering the atmosphere. Furthermore, molecular sieves with their topological structure have moderate specific surface area and pore size, good stability, and simple preparation methods, making them a research hotspot in the field of carbon dioxide adsorption. However, existing molecular sieve powders have low adsorption capacity for weakly acidic carbon dioxide, thus necessitating a more efficient adsorbent for carbon dioxide adsorption. Summary of the Invention

[0003] To address the shortcomings of existing technologies, the present invention aims to provide a method for preparing GQDs-doped molecular sieves that efficiently adsorb carbon dioxide, which has the advantage of improving the adsorption capacity of molecular sieves for carbon dioxide.

[0004] The above-mentioned objective of this invention is achieved through the following technical solution: a method for preparing GQDs-doped molecular sieves for efficient carbon dioxide adsorption, comprising the following steps:

[0005] S1. Dissolve aluminum chloride, sodium silicate, and potassium silicate in deionized water and stir to obtain a precursor solution;

[0006] S2. The dissolved precursor solution is subjected to ultrasonic treatment;

[0007] S3. Add N-GQDs to the precursor solution, stir again, and then place it in a reactor for hydrothermal reaction.

[0008] S4. After the reaction is complete, the solution is centrifuged, washed, dried and ground to obtain GQDs-doped molecular sieves.

[0009] Preferably, the quantum dots in S3 are nitrogen-doped graphene quantum dots.

[0010] Preferably, the nitrogen-doped graphene quantum dots comprise 0.1%-2% of the soluble salt source by mass.

[0011] Preferably, the hydrothermal reaction in S3 is carried out at a temperature of 150-200°C for 10-25 hours.

[0012] Preferably, the stirring process in S3 is magnetic stirring.

[0013] Preferably, the stirring time in step S3 is 4-5 hours, and the stirring temperature is 20-30°C.

[0014] Preferably, the stirring process in step S3 is followed by ultrasonic treatment.

[0015] Preferably, the ultrasonic treatment time in S3 is 15 minutes, and the ultrasonic temperature is 20-30°C.

[0016] In summary, the present invention has at least one of the following beneficial technical effects:

[0017] 1. This invention provides a method for preparing GQDs-doped molecular sieves with high-efficiency carbon dioxide adsorption performance. The method involves mixing and dissolving an aluminum source, a silicon source, and quantum dots. The oxygen-containing functional groups on the surface of graphene quantum dots interact with the molecular sieve precursor, influencing the nucleation and growth of the molecular sieve. The nitrogen-containing functional groups on the surface of N-doped graphene quantum dots (N-GQDs) provide alkalinity and positive charge, thereby improving the carbon dioxide adsorption capacity. The N-GQDs-doped molecular sieve provided by this invention exhibits good CO2 adsorption capacity.

[0018] 2. The preparation method provided by this invention is simple, has low requirements, is easy to operate, and has low cost. It saves a lot of industrial-grade raw materials, does not require chemical reagents or purification, and greatly reduces environmental pollution.

[0019] 3. The N-GQDs doped molecular sieves provided by this invention have a wide range of applications, including ion exchange, catalysis, and adsorption.

[0020] 4. The doped molecular sieve provided by this invention, after surface modification, exhibits a stronger affinity and adsorption capacity for carbon dioxide molecules. Graphene quantum dots (GQDs) possess a large specific surface area and abundant edge active sites, providing more adsorption sites for carbon dioxide molecules, making them easier to capture. In particular, element-doped GQDs can also regulate the surface chemical properties of the molecular sieve, such as charge polarity, surface acidity / alkalinity, and the internal pore structure, making it more conducive to the diffusion and adsorption of carbon dioxide molecules. GQDs have excellent electrical properties and can act as a medium for electron transfer during adsorption, accelerating electron transfer between carbon dioxide molecules and the molecular sieve, thereby enhancing the adsorption force and improving adsorption performance. Attached Figure Description

[0021] Figure 1 This is a flowchart of the preparation method of the present invention;

[0022] Figure 2 The X-ray diffraction pattern of the molecular sieve with 0% GQDs added in Example 1;

[0023] Figure 3 This is a scanning electron microscope image of the molecular sieve with 0% GQDs added in Example 1;

[0024] Figure 4 This is a graph showing the carbon dioxide adsorption curve of the molecular sieve with 0% GQDs added in Example 1;

[0025] Figure 5 The X-ray diffraction pattern of the molecular sieve with 0.5% GQDs added in Example 2;

[0026] Figure 6 The image shows a scanning electron microscope image of the molecular sieve with 0.5% GQDs added in Example 2.

[0027] Figure 7 The graph shows the carbon dioxide adsorption curve of the molecular sieve with 0.5% GQDs added in Example 2. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. Based on the described embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0029] The following is in conjunction with the appendix Figure 1-7 The present invention will be described in further detail below.

[0030] Example 1:

[0031] Weigh out 1.2692 g of aluminum chloride (AlCl3·H2O, 98% by mass), 0.5625 g of sodium silicate (Na2SiO3·9H2O), and 0.6910 g of potassium silicate (K2SiO3·xH2O), dissolve them in 35 mL of deionized water, and then sonicate the solution for 15 min at a temperature of 20–30 °C and a frequency of 30 kHz. Add 0% graphene quantum dots (N-GQDs), and then magnetically stir the mixture for 4–5 h at a temperature of 20–30 °C. The solution was then sonicated for 15 minutes at a temperature of 20–30°C. The sonicated solution was then transferred to a hydrothermal reactor for a hydrothermal reaction at 200°C for 24 hours. After the reaction, the solution was centrifuged at 10,000 rpm for 15 minutes, and washed 3–5 times. The washed product was then dried at 60°C for 8–12 hours. The dried product was then ground into powder to obtain 0% GQDs-doped molecular sieves and undoped molecular sieves.

[0032] The molecular sieve with 0% GQD added has a specific surface area of ​​428 m². 2 / g, pore volume 0.20cm³ 3 The molecular sieve prepared in this example was subjected to X-ray diffraction, with a pore size of 2.0 nm and a CO2 adsorption capacity of 1.03 mmol / g. Figure 2 As shown, the diffraction peaks indicate a silica phase structure. The molecular sieve prepared in this embodiment was subjected to electron scanning, and the resulting electron micrograph is shown below. Figure 3 As shown, the powder particles are relatively large. The molecular sieve prepared in this embodiment was subjected to CO2 adsorption testing, and the resulting adsorption curve is shown below. Figure 4 As shown, the maximum adsorption capacity is 1.03 mmol / g.

[0033] Example 2:

[0034] Weigh out 1.2692 g of aluminum chloride (AlCl3·H2O, 98% by mass), 0.5625 g of sodium silicate (Na2SiO3·9H2O), and 0.6910 g of potassium silicate (K2SiO3·xH2O), dissolve them in 35 mL of deionized water, and then sonicate the solution for 15 min at a temperature of 20–30 °C and a frequency of 30 kHz. Add 0.2% nitrogen-doped graphene quantum dots (N-GQDs), and then magnetically stir the mixture at 50 rpm for 4–5 h at a temperature of 20–30 °C. After stirring, sonicate the solution for 15 min at a temperature of 20–30 °C and a frequency of 30 kHz. Then transfer the solution to a hydrothermal reactor for a hydrothermal reaction at 200 °C for 24 h. After the reaction is complete, the solution is centrifuged at 10,000 rpm for 15 min and washed 3 to 5 times. The centrifuged product is then dried at 60°C for 8 to 12 h. The dried product is then ground into powder to obtain GQDs-doped molecular sieves.

[0035] Its specific surface area is 513 m². 2 / g, pore volume is 0.28cm³ 3 The molecular sieve prepared in this example was subjected to X-ray diffraction, with a pore size of 3.51 nm and a CO2 adsorption capacity of 1.35 mmol / g. Figure 5 As shown, the diffraction peaks indicate a silica phase structure. The molecular sieve prepared in this embodiment was subjected to electron scanning, and the resulting electron micrograph is shown below. Figure 6 As shown, its surface exhibits irregular pores of approximately 3.5 nm. The molecular sieve prepared in this embodiment was subjected to CO2 adsorption testing, and the resulting adsorption curve is shown below. Figure 7 As shown, the maximum adsorption capacity is 1.35 mmol / g.

[0036] Example 3:

[0037] Weigh out 1.2692 g of aluminum chloride (AlCl3·H2O, 98% by mass), 0.5625 g of sodium silicate (Na2SiO3·9H2O), and 0.6910 g of potassium silicate (K2SiO3·xH2O), dissolve them in 35 mL of deionized water, and then sonicate them for 15 min at a temperature of 20–30 °C and a frequency of 30 kHz. Add 2% nitrogen-doped graphene quantum dots (N-GQDs), and magnetically stir the mixture at 50 rpm for 4–5 h at a temperature of 20–30 °C. After stirring, sonicate the solution for 15 min at a temperature of 20–30 °C and a frequency of 30 kHz. Then transfer the solution to a hydrothermal reactor for a hydrothermal reaction at 150 °C for 10 h. After the reaction is complete, the solution is centrifuged at 10,000 rpm for 15 min and washed 3 to 5 times. The centrifuged product is then dried at 60°C for 8 to 12 h. The dried product is then ground into powder to obtain GQDs-doped molecular sieves.

[0038] Its specific surface area is 431 m². 2 / g, pore volume is 0.40cm³ 3 / g, with a pore size of 4.5nm, and a CO2 adsorption capacity of 1.10mmol / g.

[0039] Example 4:

[0040] Weigh out 1.2692 g of aluminum chloride (AlCl3·H2O, 98% by mass), 0.5625 g of sodium silicate (Na2SiO3·9H2O), and 0.6910 g of potassium silicate (K2SiO3·xH2O), dissolve them in 35 mL of deionized water, and then sonicate them for 15 min at a temperature of 20–30 °C and a frequency of 30 kHz. Add 1% nitrogen-doped graphene quantum dots (N-GQDs), and magnetically stir the mixture at 50 rpm for 4–5 h at a temperature of 20–30 °C. After stirring, sonicate the solution for 15 min at a temperature of 20–30 °C and a frequency of 30 kHz. Then transfer the solution to a hydrothermal reactor for a hydrothermal reaction at 180 °C for 18 h. After the reaction is complete, the solution is centrifuged at 10,000 rpm for 15 min and washed 3 to 5 times. The centrifuged product is then dried at 60°C for 8 to 12 h. The dried product is then ground into powder to obtain GQDs-doped molecular sieves.

[0041] Its specific surface area is 499m² 2 / g, pore volume is 0.22cm³ 3 / g, with a pore size of 3.3nm, and a CO2 adsorption capacity of 1.15mmol / g.

[0042] In summary, the performance comparison table of the GQDs-doped molecular sieves prepared in Examples 1-4 is as follows:

[0043]

[0044] The rate of change is calculated as follows: based on the data in Example 1, the formula is: (Value of Example (2 or 3 or 4) - Value of Example 1) / Value of Example 1 × 100%. A positive sign indicates an increase, and a negative sign indicates a decrease (but in this data, the parameters of Examples 2-4 are all increased compared to those in Example 1).

[0045] Example 2: Significant improvements were observed in all parameters, especially pore size (+75.5%) and CO2 adsorption capacity (+31.1%), indicating that the addition of GQD effectively optimized the pore structure and adsorption performance.

[0046] Example 3: The pore volume and pore size increased the most (+100.0% and +125.0%, respectively), but the specific surface area and CO2 adsorption capacity increased less, which may be related to the slightly lower adsorption efficiency caused by the large pore size (but still higher than Example 1).

[0047] Example 4: The specific surface area and CO2 adsorption capacity are significantly improved, but the pore volume and pore size are moderately improved, resulting in a balanced overall performance.

[0048] Overall trend: The pore size of Examples 2-4 all increased (2.0 nm → 3.3 ~ 4.5 nm), which is related to the increase in pore volume and CO2 adsorption capacity, indicating that larger pore size is beneficial to gas adsorption.

[0049] In summary, the CO2 adsorption capacity of the molecular sieve doped with GQDs obtained by the preparation method disclosed in this application is 1.07-1.31 times that of the molecular sieve without added GQDs, which significantly improves the adsorption performance of the molecular sieve for CO2.

[0050] The embodiments described herein are preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Therefore, all equivalent changes made in accordance with the structure, shape, and principle of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing GQDs-doped molecular sieves for efficient carbon dioxide adsorption, characterized in that, Includes the following steps: S1. Dissolve aluminum chloride, sodium silicate, and potassium silicate in deionized water and stir to obtain a precursor solution; S2. The dissolved precursor solution is subjected to ultrasonic treatment; S3. Add N-GQDs to the precursor solution, stir again, and then place it in a reactor for hydrothermal reaction. S4. After the reaction is complete, the solution is centrifuged, washed, dried and ground to obtain GQDs-doped molecular sieves.

2. The method for preparing a GQDs-doped molecular sieve for high-efficiency carbon dioxide adsorption according to claim 1, characterized in that, The quantum dots mentioned in S3 are nitrogen-doped graphene quantum dots.

3. The method for preparing a GQDs-doped molecular sieve for high-efficiency carbon dioxide adsorption according to claim 2, characterized in that, The mass percentage of nitrogen-doped graphene quantum dots to soluble salt sources is 0.1%-2%.

4. The method for preparing a GQDs-doped molecular sieve for high-efficiency carbon dioxide adsorption according to claim 1, characterized in that, The hydrothermal reaction in S3 is carried out at a temperature of 150-200℃ for a reaction time of 10-25 hours.

5. The method for preparing a GQDs-doped molecular sieve for high-efficiency carbon dioxide adsorption according to claim 1, characterized in that, The stirring method in S3 is magnetic stirring.

6. A method for preparing a GQDs-doped molecular sieve for efficient carbon dioxide adsorption according to claim 1 or 5, characterized in that, The stirring time in S3 is 4-5 hours, and the stirring temperature is 20-30℃.

7. The method for preparing a GQDs-doped molecular sieve for high-efficiency carbon dioxide adsorption according to claim 6, characterized in that, The mixture in step S3 is then subjected to ultrasonic treatment after stirring.

8. The method for preparing a GQDs-doped molecular sieve for high-efficiency carbon dioxide adsorption according to claim 7, characterized in that, The ultrasonic treatment time in S3 is 15 minutes, and the ultrasonic temperature is 20-30℃.

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