Organic amine modified HMS molecular sieve and its application in carbon dioxide capture

Abstract

The application discloses an organic amine modified HMS molecular sieve and application thereof in carbon dioxide capture, and specifically relates to the following steps: first, preparing mesoporous molecular sieve HMS, which contains two kinds of pore structures, 4.5-8.0 nm and 11.5-17.5 nm respectively, and a single wide diffraction peak is presented at 2theta=2.6 degrees in X-ray powder diffraction; then, grafting amino silane on the surface of the mesoporous molecular sieve HMS; and finally, immersing the mesoporous molecular sieve HMS in an organic amine solution to obtain a multilevel organic amine modified HMS molecular sieve. The synthesis method is simple, the carbon dioxide adsorption efficiency is high, and the thermal stability is good.

Description

Technical Field

[0001] This invention relates to an organic amine-modified HMS molecular sieve and its application in carbon dioxide capture, belonging to the field of carbon dioxide capture materials technology. Background Technology

[0002] Silica is one of the most abundant materials discovered in the world, existing in many different minerals in various environments. In nature, SiO2 usually exists in the form of quartz, a major component of sand, which accounts for more than 10% of the Earth's crust. SiO2 synthesis is relatively easy, and synthesized silica typically possesses high specific surface area and porosity. The structural characteristics of silica can be controlled through appropriate modifications during the synthesis process. Mesoporous silica, with its large pore volume, tunable pore size, high surface area, and ease of modification, is an excellent choice as an adsorbent. Despite its attractive structural characteristics, unmodified silica adsorbents do not exhibit high CO2 adsorption efficiency. Fortunately, the surface of silica contains a large number of Si-OH groups, providing the necessary conditions for introducing functional groups conducive to carbon dioxide capture. Because amines are inherently basic, loading amino groups onto silica supports helps provide high-affinity active sites for CO2, facilitating carbon dioxide capture. For amine-supported silica adsorbents, it is necessary to select a suitable precursor and modify the silica support itself to ensure good performance of the amino solid adsorbent. Regarding amine screening, Song et al. reported the introduction of branched polyvinyl alcohol into MCM-41 via wet impregnation (Energy & Fuels, 2002, 16(6), 1463-1469). They observed that, under a pure carbon dioxide atmosphere and at 75°C, the carbon dioxide adsorption capacity of the modified adsorbent increased from 8.6 mg g / L of the support MCM-41. -1 Increased to 112 mg g -1Ahmed et al. investigated the adsorption capacity of MCM-41 impregnated with ethanolamine (MEA), diethanolamine (DEA), and triethanolamine (TEA) (International Journal of Greenhouse Gas Control, 2016, 51, 230-238) to better understand the effect of different amine types on adsorbent performance. Under the same conditions, the adsorption capacity was in the order of MEA (primary amine) > DEA (secondary amine) > TEA (tertiary amine). Lai et al. developed an amine (aminoethylethanolamine) impregnated silica adsorbent for capturing carbon dioxide from flue gas (Applied Energy, 2018, 223, 293-301). Under the conditions of 25 °C, 10% CO2, and 10% H2O, the saturated adsorption capacity of the aminosilicic acid adsorbent impregnated with 55 wt% AEEA was 4.54 mmol g. -1 . Summary of the Invention

[0003] The purpose of this invention is to provide an organic amine-modified HMS molecular sieve and its application in carbon dioxide capture. By constructing a special pore structure, the invention mainly solves the problems of pore blockage and agglomeration caused by too much modifier, thereby increasing the amine loading and improving the carbon dioxide adsorption performance.

[0004] The implementation process of this invention is as follows:

[0005] A method for preparing multi-level organic amine-modified HMS molecular sieves includes the following steps:

[0006] (1) Mesoporous molecular sieve HMS was prepared, which contains two pore structures with pore sizes of 4.5–8.0 nm and 11.5–17.5 nm, respectively. X-ray powder diffraction showed a single-width diffraction peak at 2θ = 2.6º.

[0007] (2) Grafting aminosilane onto the surface of the multi-level mesoporous molecular sieve HMS prepared in step (1);

[0008] (3) The HMS molecular sieve grafted with aminosilane in step (2) is impregnated in an organic amine solution.

[0009] In the above-mentioned method for preparing multi-level organic amine modified HMS molecular sieves, the aminosilane is selected from (3-aminopropyl)trimethoxysilane, (3-aminopropyl)triethoxysilane, 3-aminopropylmethyldiethoxysilane, N-(2-aminoethyl)-3-aminopropylmethyldiethoxysilane, and 3-aminopropylmethyldiethoxysilane.

[0010] In the above-mentioned method for preparing multi-level organic amine modified HMS molecular sieves, the organic amine is selected from tetraethylenepentamine, polyethyleneimine, hexadecamide ethanol, pentaethylenehexamine, and tris(2-aminoethyl)amine.

[0011] In the above-mentioned preparation method of multi-level organic amine modified HMS molecular sieve, the synthesis method of mesoporous molecular sieve HMS in step (1) is as follows: the template agent poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymer is added to a 25-35 wt% hydrochloric acid solution, stirred until clear, and then heated to 35-60°C to add tetraethyl silicate. After stirring thoroughly, the product is subjected to hydrothermal reaction at 80-140°C. The product is calcined at 500-600°C to remove the template agent to obtain mesoporous molecular sieve HMS. The molar ratio of template agent to tetraethyl silicate is 1:40-80.

[0012] In the above-mentioned method for preparing multi-level organic amine modified HMS molecular sieve, in step (2), before grafting aminosilane onto the surface of the mesoporous molecular sieve HMS, the mesoporous molecular sieve HMS is activated at 100-150℃.

[0013] In the above-mentioned method for preparing multi-level organic amine modified HMS molecular sieve, in step (2), under nitrogen protection, the mesoporous molecular sieve HMS is added to a polar organic solvent of aminosilane for reflux treatment. The polar organic solvent is selected from toluene, ethanol, methanol, and acetonitrile, with toluene being the most preferred.

[0014] Compared with the prior art, the advantages of the present invention are:

[0015] (1) By optimizing the molecular sieve synthesis conditions and steps, this invention successfully synthesized HMS, a multi-level mesoporous molecular sieve with high specific surface area, large pore volume and good thermal stability.

[0016] (2) In this invention, under nitrogen protection, the silanol aminosilane on the surface of the molecular sieve is uniformly loaded onto the surface of the molecular sieve by chemical grafting, and then organic amine is introduced into the molecular sieve pores by physical impregnation. The steric hindrance effect of the two amine modifiers is used to avoid agglomeration and pore blockage, thereby improving the adsorption performance of carbon dioxide.

[0017] (3) The present invention improves the amine content through a bifunctional method, thus avoiding the impact of the volatilization of traditional liquid amine absorbents on equipment corrosion;

[0018] (4) The present invention is simple and feasible to synthesize and is easy to carry out industrial production. The adsorbent retains the original skeleton after bifunctionalization, which greatly improves the amine loading and solves the problems of pore blockage and agglomeration caused by the modifier. It has high adsorption capacity and selectivity for carbon dioxide, and has good thermal stability and recycling ability. Attached Figure Description

[0019] Figure 1 XRD patterns of modified and unmodified molecular sieve adsorbents;

[0020] Figure 2 Nitrogen adsorption-desorption curves (left) and pore size distribution (right) of modified and unmodified molecular sieve adsorbents.

[0021] Figure 3 Thermogravimetric curves of modified and unmodified molecular sieve adsorbents;

[0022] Figure 4 Breakthrough adsorption curves of modified and unmodified molecular sieve adsorbents;

[0023] Figure 5 Cyclic regeneration diagram of bifunctional adsorbent. Detailed Implementation

[0024] To make the above-described objects, features, and advantages of the present invention more apparent and understandable, the present invention will be described in detail with reference to the following specific embodiments. It should be noted that the following embodiments are only for illustrating the implementation methods and typical parameters of the present invention and are not intended to limit the range of parameters described in the present invention. Reasonable modifications derived therefrom are still within the scope of protection of the claims of the present invention. It should be noted that the endpoints of the range and any values ​​disclosed herein are not limited to the precise range or value, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the range, the endpoint values ​​of the range combined with the single point value, and the single point value can be combined to obtain one or more new numerical ranges, which are considered to be specifically disclosed herein.

[0025] Example 1 Synthesis of bifunctionalized multilevel mesoporous molecular sieve HMS

[0026] (1) Synthesis of multi-level mesoporous molecular sieve HMS

[0027] The template agent, a poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymer, was added to an HCl solution (26.8 wt%). After stirring at room temperature until clear, the solution was heated to 40°C, and 2.14 g of tetraethyl silicate was added. Stirring continued for 4.5 h, followed by the addition of another 2.14 g of tetraethyl silicate for 24 h. The mixture was then hydrothermally heated at 100°C for 24 h. The sample was filtered and dried, and finally calcined in a muffle furnace at 550°C for 4 h to obtain the multilayer mesoporous molecular sieve HMS.

[0028] (2) Grafting (3-aminopropyl)trimethoxysilane

[0029] 0.5 g of the prepared multilayer mesoporous molecular sieve HMS was pretreated in an oven at 120 °C for 12 h to remove moisture and impurity gases. Then, 0.5 g of HMS was dispersed in 50 mL of toluene under vacuum and stirred for 30 min under nitrogen protection. Next, 0.5 mL of (3-aminopropyl)trimethoxysilane was added to the mixture, and the mixture was refluxed at 80 °C for 12 h. After the reaction was complete, the cooled product was repeatedly washed with toluene and ethanol, and then dried at 60 °C to obtain the grafted adsorbent HMS-100A.

[0030] (3) Bifunctional multi-level mesoporous molecular sieve HMS

[0031] 70% tetraethylenepentamine was dissolved in 30 mL of ethanol and stirred at room temperature for 30 min. Then, the sample HMS-100A prepared above was added to the solution. The temperature was adjusted to 40℃ and stirred continuously until a slurry was formed. Then, the solution was placed in a forced-air drying oven and evaporated and dried at 85℃ for 10 h to obtain the bifunctional adsorbent HMS-100A-70T.

[0032] 70% tetraethylenepentamine was dissolved in 30 mL of ethanol and stirred at room temperature for 30 min. Then, multi-layered mesoporous molecular sieve HMS was added to the solution. The temperature was adjusted to 40℃ and stirred continuously until a slurry was formed. The slurry was then placed in a forced-air drying oven and evaporated and dried at 85℃ for 10 h to obtain the impregnated adsorbent HMS-70T. Example 2

[0033] Similar to Example 1, except that the grafting solvent is ethanol. When toluene is used as the grafting solvent, the nitrogen content of adsorbent HMS-100A is 4.09 mmol g. -1 When ethanol is used as the grafting solvent, the nitrogen content is 1.88 mmol g. -1 .

[0034] Figure 1 The XRD patterns of the modified and unmodified molecular sieve adsorbents show that after chemical grafting, physical impregnation and dual modification, the static structure and morphology of the molecular sieve HMS are almost unchanged, indicating that the modification method does not change the original framework of the molecular sieve.

[0035] Figure 2The nitrogen adsorption-desorption curves (left) and pore size distribution diagrams (right) of the modified and unmodified molecular sieve adsorbents show that after chemical grafting, physical impregnation, and dual modification, the hysteresis loop gradually decreases, and the pore size initially decreases from a small size to disappear, indicating the successful synthesis of the multi-level mesoporous molecular sieve HMS. As the modification content increases, the hysteresis loop decreases, and the pore size also gradually decreases, indicating that the modifier is successfully loaded onto the carrier.

[0036] Figure 3 Thermogravimetric analysis of modified and unmodified molecular sieve adsorbents showed that HMS molecular sieve exhibited almost no mass loss and good thermal stability within 800°C. With increasing modification content, the grafted adsorbent showed significant mass loss at 500–600°C, due to the thermal decomposition of (3-aminopropyl)trimethoxysilane. The impregnated adsorbent showed significant mass loss at 200–350°C, due to the thermal decomposition of tetraethylenepentamine. The bifunctionalized adsorbent showed significant weight loss at 200–300°C and 450–600°C, respectively, due to the thermal decomposition of (3-aminopropyl)trimethoxysilane and tetraethylenepentamine. All adsorbents exhibited good thermal stability within 110°C.

[0037] The adsorbent prepared in Example 1 was subjected to carbon dioxide adsorption experiments using a dynamic adsorption bed at 70°C. The results are shown in Figure 4; the saturated adsorption capacity of the molecular sieve HMS for carbon dioxide was 0.31 mmol g. -1 The saturated adsorption capacity of adsorbent HMS-100A is 1.57 mmol g. -1 The saturated adsorption capacity of adsorbent HMS-70T is 3.75 mmol g. -1 The saturated adsorption capacity of the bifunctional adsorbent HMS-100A-70T is 5.34 mmol g. -1 The adsorption performance increased by 5.03, 3.77, and 1.38 mmol g, respectively. -1 .

[0038] The bifunctional adsorbent prepared in Example 1 was subjected to a cyclic regeneration experiment. The results are shown in Figure 5. After 10 adsorption-desorption experiments, the adsorption performance of adsorbent HMS-100A-70T decreased by 9.8%, while retaining a high carbon dioxide adsorption capacity. This indicates that the adsorbent has good cyclic regeneration performance.

[0039] The inventors changed the type of aminosilane, using (3-aminopropyl)triethoxysilane, 3-aminopropylmethyldiethoxysilane, or N-(2-aminoethyl)-3-aminopropylmethyldiethoxysilane instead of (3-aminopropyl)trimethoxysilane, and obtained similar experimental results. Changing the type of organic amine, using polyethyleneimine, hexadecylamide ethanol, pentaethylenehexamine, or tri(2-aminoethyl)amine instead of tetraethylenepentamine, showed that the results were significantly better with tetraethylenepentamine and pentaethylenehexamine.

[0040] While this disclosure is made as described above, its scope of protection is not limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of this disclosure, and such changes and modifications will fall within the scope of protection of this invention.

Claims

1. A method for preparing organic amine-modified HMS molecular sieves, characterized in that... Includes the following steps: (1) Mesoporous molecular sieve HMS was prepared, which contained two pore structures with pore sizes of 4.5–8.0 nm and 11.5–17.5 nm, respectively. X-ray powder diffraction showed a single-width diffraction peak at 2θ = 2.6°. (2) Grafting aminosilane onto the surface of the mesoporous molecular sieve HMS prepared in step (1); (3) The HMS molecular sieve grafted with aminosilane in step (2) is impregnated in an organic amine solution.

2. The method for preparing organic amine-modified HMS molecular sieve according to claim 1, characterized in that: The aminosilane is selected from (3-aminopropyl)trimethoxysilane, (3-aminopropyl)triethoxysilane, 3-aminopropylmethyldiethoxysilane, and N-(2-aminoethyl)-3-aminopropylmethyldiethoxysilane.

3. The method for preparing organic amine-modified HMS molecular sieve according to claim 1, characterized in that: The organic amine is selected from tetraethylenepentamine, polyethyleneimine, hexadecamide ethanol, pentaethylenehexamine, and tris(2-aminoethyl)amine.

4. The method for preparing organic amine-modified HMS molecular sieve according to claim 1, characterized in that... Step (1) The method for synthesizing mesoporous molecular sieve HMS is as follows: the template agent, poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymer, is added to a 25-35 wt% hydrochloric acid solution. After stirring until clear, the temperature is raised to 35-60°C and tetraethyl silicate is added. After stirring thoroughly, a hydrothermal reaction is carried out at 80-140°C. The product is calcined at 500-600°C to remove the template agent, thereby obtaining mesoporous molecular sieve HMS. The molar ratio of the template agent to tetraethyl silicate is 1:40-80.

5. The method for preparing organic amine-modified HMS molecular sieve according to claim 1, characterized in that: In step (2), before grafting aminosilane onto the surface of the mesoporous molecular sieve HMS, the mesoporous molecular sieve HMS is activated at 100-150℃.

6. The method for preparing organic amine-modified HMS molecular sieve according to claim 1, characterized in that: In step (2), under nitrogen protection, the mesoporous molecular sieve HMS is added to a polar organic solvent containing aminosilane and refluxed.

7. The method for preparing organic amine-modified HMS molecular sieve according to claim 6, characterized in that: The polar organic solvent is selected from toluene, ethanol, methanol, and acetonitrile.

8. The method for preparing organic amine-modified HMS molecular sieve according to claim 7, characterized in that: The polar organic solvent is toluene.

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