A method for preparing a modified molecular sieve adsorbent

Abstract

The application provides a preparation method of a modified molecular sieve adsorbent, wherein the molecular sieve is subjected to channel modification, and then subjected to amine modification; after the two modifications, carbon dioxide is adsorbed, and the carbon dioxide adsorption capacity is 4.0 mmol / g or more; the used adsorbent can be recycled for use, and the used adsorbent can be subjected to desorption treatment and reused, so that the problems such as low consumption and no solvent loss are solved; and the traditional absorption method is overcome, and the problems such as high energy consumption, solvent loss and recovery are solved.

Description

Technical Field

[0001] This invention belongs to the field of gas adsorption technology, specifically, it is a method for preparing a modified molecular sieve adsorbent. Background Technology

[0002] Carbon dioxide emissions mainly originate from the combustion and conversion processes of fossil fuels (coal, oil, natural gas, etc.). With the establishment of my country's dual-carbon targets, carbon capture and storage (CCS) of CO2 emissions from various industries is of great significance.

[0003] Methods for capturing carbon dioxide mainly include absorption, adsorption, membrane separation, and cryogenic freezing. Currently, absorption is the most mature and widely used carbon dioxide capture technology, but it consumes a lot of energy, and the problems of solvent loss and recovery urgently need to be solved. Membrane separation has drawbacks such as high membrane manufacturing costs, susceptibility to scaling leading to low permeability during operation, and instability in humid environments. Adsorption methods utilize recyclable adsorbents, are suitable for low CO2 concentration gas streams, and are relatively easy to separate, leading to extensive research in recent years. However, the low CO2 adsorption capacity of solid adsorbents presents challenges for their industrial application.

[0004] Molecular sieves have been extensively studied as catalysts. In recent years, their unique morphology and structure have led to increased research on their use as CO2 adsorbents. Modified molecular sieves as adsorbents will be a key focus of future research.

[0005] Chinese Patent CN201310509561.X discloses a ZSM-5 molecular sieve modified catalyst and its preparation method. The catalyst is prepared by grafting groups and modifying the surface of ZSM-5 molecular sieve as a support, and is used in a fixed-bed reactor for the preparation of ethylene from low-concentration acetic acid dehydration.

[0006] Chinese patent CN202210261958.0 discloses a modified molecular sieve for CO2 adsorption and separation, and its preparation method and apparatus. The method involves vacuum degassing and activating the molecular sieve, depositing an organic amine onto the sieve, and then vacuum degassing to obtain the modified molecular sieve. This method employs vacuum gas-phase stepwise dynamic deposition, overcoming the shortcomings of traditional organic amine impregnation methods, such as uneven loading and easy pore blockage. It also eliminates waste liquid and is easily mass-produced industrially.

[0007] Chinese patent CN202211600250.X discloses a Zn-MOR molecular sieve and its application in adsorbing and separating CO2 from low-carbon hydrocarbons. The method involves mixing zinc salt, sodium aluminate, sodium hydroxide, silicon source, and water, and then hydrothermally crystallizing the resulting gel to obtain a zinc-containing MOR heteroatom molecular sieve. The synthesis process is simple and the product cost is low. It is the first molecular sieve material to achieve CO2 / C2H2 capture of CO2. Summary of the Invention

[0008] The purpose of this invention is to provide a method for preparing a modified molecular sieve adsorbent. The molecular sieve is modified by modifying its pores and then by amine modification. After two modifications, a carbon dioxide adsorption test is conducted, and the carbon dioxide adsorption capacity is above 4.0 mmol / g. The adsorbent can be recycled multiple times, and the used adsorbent can be desorbed and reused.

[0009] This invention provides a method for preparing a molecular sieve adsorbent. The molecular sieve support is pretreated, modified in terms of pores, loaded once, and loaded twice to obtain a molecular sieve adsorbent for adsorbing CO2 gas.

[0010] Generally, the preparation steps of the molecular sieve adsorbent are as follows:

[0011] (1) Pretreatment: The molecular sieve carrier is acid washed with a mass ratio of molecular sieve carrier to acid of 1:0.5-1:10. After stirring for 0.5 h-3 h, it is washed with distilled water until neutral, filtered, and dried.

[0012] (2) Modified molecular sieve: The pore size of the pretreated molecular sieve is changed and the internal pores are modified. It is modified with a modifier. The treatment temperature is 5℃-100℃, the treatment time is 0.5 h-8 h, the immersion time is 0.5 h-24 h, the modified molecular sieve is washed until neutral, filtered, and dried.

[0013] (3) First loading of molecular sieve: Under microwave induction, the modified molecular sieve is loaded with amine solution, stirred and allowed to stand for 0.5 h-8 h; the same type of amine solution is added again for loading, stirred and allowed to stand for the same time, microwave induction is stopped, filtered and dried.

[0014] (4) Secondary loaded molecular sieve: The molecular sieve after primary loading is ultrasonically loaded with aminosilane solvent, filtered and dried to prepare molecular sieve adsorbent.

[0015] Preferably, the acid mentioned in step (1) includes nitric acid, sulfuric acid, and hydrochloric acid.

[0016] The modifier mentioned in step (2) is one of hydrogen peroxide, phosphoric acid, sodium hypochlorite, perchloric acid, sodium hydroxide, and potassium hydroxide.

[0017] The molecular sieve is of type MCM-41, ZSM-5, SAPO-34, MOR, or NaY.

[0018] The microwave power mentioned in step (3) is 600~800W, and the microwave radiation time is 5-10 min.

[0019] The amine solution mentioned in step (3) is at least one of monoethanolamine, diethanolamine, diethylenetriamine, triethanolamine, diisopropanolamine, 2-aminoisobutanol, N-methylmonoethanolamine, and N-methyldiethanolamine.

[0020] The aminosilane mentioned in step (4) is one of bis(dimethylaminodimethylsilane) or aminopropyltriethoxysilane.

[0021] In step (4), the ultrasonic dispersion loading time is 30 min-60 min, and the ultrasonic dispersion loading temperature is 50℃-80℃.

[0022] The molecular sieve adsorbent prepared by the method of the present invention can be used to adsorb CO2 gas. CO2 is adsorbed in a fixed-bed reactor containing a glass adsorption column, and the CO2 content at the inlet and outlet is measured by gas chromatography.

[0023] The method for preparing modified molecular sieve adsorbent provided by this invention involves modifying the pores of the molecular sieve, followed by amine modification. After two modifications, a carbon dioxide adsorption test is conducted, and the carbon dioxide adsorption capacity is above 4.0 mmol / g. The adsorbent can be recycled multiple times, and the used adsorbent can be desorbed and reused. This method has low consumption and no solvent loss, overcoming the problems of high energy consumption and solvent loss and recovery associated with traditional absorption methods. Implementation

[0024] The present invention will now be described in detail with reference to the embodiments. Example 1

[0025] Preparation of molecular sieve adsorbents:

[0026] (1) Pretreatment: Take 10g of ZSM-5 molecular sieve, add 50mL of 20% nitric acid, stir with a magnetic stirrer for 0.5h, wash with distilled water until neutral, filter and dry;

[0027] (2) Modified molecular sieve: Add 100 mL of 30% H2O2 and stir at 20℃ for 2 h, then impregnate for 20 h, wash until neutral, and dry at 150℃;

[0028] (3) First loading of molecular sieve: Adjust the microwave power to 800W, put the modified molecular sieve into 20mL of monoethanolamine solution, stir with a magnetic stirrer for 10min, let stand for 4h, add another 10mL of monoethanolamine solution, stir with a magnetic stirrer for 10min, let stand for 4h, stop microwave induction, filter and dry.

[0029] (4) Secondary loading of molecular sieve: The molecular sieve after primary loading is placed in 10 mL of bis(dimethylaminodimethylsilane) solution for ultrasonic loading. The ultrasonic loading temperature is 60℃ and the ultrasonic loading time is 30 min. After filtration and drying, the molecular sieve adsorbent is prepared.

[0030] CO2 adsorption:

[0031] The fixed-bed reactor contains a glass adsorption column, the temperature of which is controlled by a heating furnace. During adsorption, 10 g of molecular sieve adsorbent is packed into the adsorption column, and a dry CO2 / N2 mixture (CO2 content 12.5 wt%) is passed through the pipeline at a flow rate of 40 mL / min. The CO2 content at the inlet and outlet is measured by gas chromatography. The CO2 adsorption capacity is 4.8 mmol / g. Example 2

[0032] Preparation of molecular sieve adsorbents:

[0033] (1) Pretreatment: Take 10g of ZSM-5 molecular sieve, add 50mL of 10% hydrochloric acid, stir with a magnetic stirrer at 20℃ for 3h, wash with distilled water to reach neutrality, filter and dry.

[0034] (2) Modified molecular sieve: Add 100 mL of 30% H2O2 and stir at 40 °C for 4 h, then impregnate for 24 h, wash until neutral, and dry at 150 °C;

[0035] (3) First loading of molecular sieve: Adjust the microwave power to 800W, put the modified molecular sieve into 20mL of diethanolamine solution, stir with a magnetic stirrer for 5min, let stand for 0.5h, add 10mL of monoethanolamine solution again, stir with a magnetic stirrer for 5min, let stand for 0.5h, stop microwave induction, filter and dry.

[0036] (4) Secondary loading of molecular sieve: The molecular sieve after primary loading is placed in 10 mL of aminopropyltriethoxysilane solution for ultrasonic loading. The ultrasonic loading temperature is 50 °C and the ultrasonic loading time is 40 min. After filtration and drying, the molecular sieve adsorbent is prepared.

[0037] CO2 adsorption:

[0038] The fixed-bed reactor contains a glass adsorption column, the temperature of which is controlled by a heating furnace. During adsorption, 10 g of molecular sieve adsorbent is packed into the adsorption column, and a dry CO2 / N2 mixture (CO2 content 12.5 wt%) is passed through the pipeline at a flow rate of 40 mL / min. The CO2 content at the inlet and outlet is measured by gas chromatography. The CO2 adsorption capacity is 4.5 mmol / g. Example 3

[0039] Preparation of molecular sieve adsorbents:

[0040] (1) Pretreatment: Take 10g of ZSM-5 molecular sieve, add 100mL of 20% nitric acid, stir with a magnetic stirrer at 20℃ for 1h, wash with distilled water to reach neutrality, filter and dry;

[0041] (2) Modified molecular sieve: Add 100 mL of 30% H2O2 and stir at 40 °C for 6 h, then impregnate for 0.5 h, wash until neutral, and dry at 150 °C;

[0042] (3) First loading of molecular sieve: Adjust the microwave power to 800W, put the modified molecular sieve into 20mL of triethylenetriamine solution, stir with a magnetic stirrer for 10min, let stand for 8h, add another 10mL of triethylenetriamine solution, stir with a magnetic stirrer for 10min, let stand for 8h, stop microwave induction, filter and dry.

[0043] (4) Secondary loading of molecular sieve: The molecular sieve after primary loading is placed in 10 mL of aminopropyltriethoxysilane solution for ultrasonic loading. The ultrasonic loading temperature is 70 °C and the ultrasonic time is 50 min. After filtration and drying, the molecular sieve adsorbent is prepared.

[0044] CO2 adsorption:

[0045] The fixed-bed reactor contains a glass adsorption column, the temperature of which is controlled by a heating furnace. During adsorption, 10 g of molecular sieve adsorbent is packed into the adsorption column, and a dry CO2 / N2 mixture (CO2 content 12.5 wt%) is passed through the pipeline at a flow rate of 40 mL / min. The CO2 content at the inlet and outlet is measured by gas chromatography. The CO2 adsorption capacity is 4.7 mmol / g. Example 4

[0046] Preparation of molecular sieve adsorbents:

[0047] (1) Pretreatment: Take 10g of ZSM-5 molecular sieve, add 50mL of 5% nitric acid, stir with a magnetic stirrer at 20℃ for 2h, wash with distilled water until neutral, filter and dry;

[0048] (2) Modified molecular sieve: Add 100 mL of 30% H2O2 and stir at 80℃ for 8 h, then impregnate for 10 h, wash until neutral, and dry at 150℃;

[0049] (3) First loading of molecular sieve: Adjust the microwave power to 600W, put the modified molecular sieve into 20mL of monoethanolamine solution, stir with a magnetic stirrer for 5min, let stand for 2h, add 10mL of monoethanolamine solution again, stir with a magnetic stirrer for 5min, let stand for 2h, stop microwave induction, filter and dry.

[0050] (4) Secondary loading of molecular sieve: The molecular sieve after primary loading is placed in 10 mL of dimethylaminodimethylsilane solution for ultrasonic loading. The ultrasonic loading temperature is 80℃ and the ultrasonic time is 60 min. After filtration and drying, the molecular sieve adsorbent is prepared.

[0051] CO2 adsorption:

[0052] The fixed-bed reactor contains a glass adsorption column, the temperature of which is controlled by a heating furnace. During adsorption, 10 g of molecular sieve adsorbent is packed into the adsorption column, and a dry CO2 / N2 mixture (CO2 content 12.5 wt%) is passed through the pipeline at a flow rate of 40 mL / min. The CO2 content at the inlet and outlet is measured by gas chromatography. The CO2 adsorption capacity is 4.8 mmol / g. Example 5

[0053] Preparation of molecular sieve adsorbents:

[0054] (1) Pretreatment: Take 10g of MCM-41 molecular sieve, add 50mL of 20% nitric acid, stir with a magnetic stirrer at 20℃ for 1.5h, wash with distilled water until neutral, filter and dry;

[0055] (2) Modified molecular sieve: Add 100 mL of 20% sodium hydroxide and stir at 100 °C for 0.5 h, then impregnate for 15 h, wash until neutral, and dry at 150 °C;

[0056] (3) First loading of molecular sieve: Adjust the microwave power to 700W, put the modified molecular sieve into 20mL of triethanolamine solution, stir with a magnetic stirrer for 8min, let stand for 4h, add 10mL of triethanolamine solution again, stir with a magnetic stirrer for 8min, let stand for 4h, stop microwave induction, filter and dry.

[0057] (4) Secondary loading of molecular sieve: The molecular sieve after primary loading is placed in 10 mL of dimethylaminodimethylsilane solution for ultrasonic loading. The ultrasonic loading temperature is 60℃ and the ultrasonic time is 30 min. After filtration and drying, the molecular sieve adsorbent is prepared.

[0058] CO2 adsorption:

[0059] The fixed-bed reactor contains a glass adsorption column, the temperature of which is controlled by a heating furnace. During adsorption, 10 g of molecular sieve adsorbent is packed into the adsorption column, and a dry CO2 / N2 mixture (CO2 content 12.5 wt%) is passed through the pipeline at a flow rate of 40 mL / min. The CO2 content at the inlet and outlet is measured by gas chromatography. The CO2 adsorption capacity is 4.0 mmol / g. Example 6

[0060] Preparation of molecular sieve adsorbents:

[0061] (1) Pretreatment: Take 10g of MCM-41 molecular sieve, add 50mL of 20% nitric acid, stir with a magnetic stirrer at 20℃ for 2.5h, wash with distilled water until neutral, filter and dry;

[0062] (2) Modified molecular sieve: Add 100 mL of 10% phosphoric acid and stir at 5°C for 3 h, then impregnate for 5 h, wash until neutral, and dry at 150°C;

[0063] (3) First loading of molecular sieve: Adjust the microwave power to 800W, put the modified molecular sieve into 20mL of N-methyldiethanolamine, stir with a magnetic stirrer for 6min, let stand for 6h, add 10mL of N-methyldiethanolamine solution again, stir with a magnetic stirrer for 6min, let stand for 6h, stop microwave induction, filter and dry.

[0064] (4) Secondary loading of molecular sieve: The molecular sieve after primary loading is placed in 10 mL of aminopropyltriethoxysilane solution for ultrasonic loading. The ultrasonic loading temperature is 60 °C and the ultrasonic time is 30 min. After filtration and drying, the molecular sieve adsorbent is prepared.

[0065] CO2 adsorption:

[0066] The fixed-bed reactor contains a glass adsorption column, the temperature of which is controlled by a heating furnace. During adsorption, 10 g of molecular sieve adsorbent is packed into the adsorption column, and a dry CO2 / N2 mixture (CO2 content 12.5 wt%) is passed through the pipeline at a flow rate of 40 mL / min. The CO2 content at the inlet and outlet is measured by gas chromatography. The CO2 adsorption capacity is 4.1 mmol / g. Example 7

[0067] Preparation of molecular sieve adsorbents:

[0068] (1) Pretreatment: Take 10g of SAPO-34 molecular sieve, add 50mL of 20% nitric acid, stir with a magnetic stirrer at 20℃ for 0.5h, wash with distilled water until neutral, filter and dry;

[0069] (2) Modified molecular sieve: Add 100 mL of 10% sodium hydroxide and stir at 20°C for 1 h, then soak for 7 h, wash until neutral, and dry at 150°C;

[0070] (3) First loading of molecular sieve: Adjust the microwave power to 800W, put the modified molecular sieve into 20mL of monoethanolamine, stir with a magnetic stirrer for 10min, let stand for 4h, add another 10mL of monoethanolamine solution, stir with a magnetic stirrer for 10min, let stand for 4h, stop microwave induction, filter and dry.

[0071] (4) Secondary loading of molecular sieve: The molecular sieve after primary loading is placed in 10 mL of dimethylaminodimethylsilane solution for ultrasonic loading. The ultrasonic loading temperature is 60℃ and the ultrasonic time is 40 min. After filtration and drying, the molecular sieve adsorbent is prepared.

[0072] CO2 adsorption:

[0073] The fixed-bed reactor contains a glass adsorption column, the temperature of which is controlled by a heating furnace. During adsorption, 10 g of molecular sieve adsorbent is packed into the adsorption column, and a dry CO2 / N2 mixture (CO2 content 12.5 wt%) is passed through the pipeline at a flow rate of 40 mL / min. The CO2 content at the inlet and outlet is measured by gas chromatography. The CO2 adsorption capacity is 4.0 mmol / g.

[0074] Comparative Example 1:

[0075] Preparation of molecular sieve adsorbents:

[0076] (1) Pretreatment: Take 10g of ZSM-5 molecular sieve, add 50mL of 20% nitric acid, stir with a magnetic stirrer for 0.5h, wash with distilled water until neutral, filter and dry;

[0077] (2) Modified molecular sieve: Add 100 mL of 30% H2O2 and stir at 20℃ for 2 h, then impregnate for 20 h, wash until neutral, and dry at 150℃;

[0078] (3) First loading of molecular sieve: Adjust the microwave power to 800W, put the modified molecular sieve into 20mL of monoethanolamine solution, stir with a magnetic stirrer for 10min, let stand for 4h, add another 10mL of monoethanolamine solution, stir with a magnetic stirrer for 10min, let stand for 4h, stop microwave induction, filter and dry.

[0079] CO2 adsorption:

[0080] The fixed-bed reactor contains a glass adsorption column, the temperature of which is controlled by a heating furnace. During adsorption, 10 g of molecular sieve adsorbent is packed into the adsorption column, and a dry CO2 / N2 mixture (CO2 content 12.5 wt%) is passed through the pipeline at a flow rate of 40 mL / min. The CO2 content at the inlet and outlet is measured by gas chromatography. The CO2 adsorption capacity is 2.0 mmol / g.

[0081] Comparative Example 2:

[0082] Preparation of molecular sieve adsorbents:

[0083] (1) Pretreatment: Take 10g of ZSM-5 molecular sieve, add 50mL of 20% nitric acid, stir with a magnetic stirrer for 0.5h, wash with distilled water until neutral, filter and dry;

[0084] (2) Modified molecular sieve: Add 100 mL of 30% H2O2 and stir at 20℃ for 2 h, then impregnate for 20 h, wash until neutral, and dry at 150℃;

[0085] (3) Primary loading of molecular sieve: Adjust the microwave power to 800W, place the modified molecular sieve in 20mL of monoethanolamine solution, stir with a magnetic stirrer for 10min, let stand for 4h, stop microwave induction, filter and dry.

[0086] (4) Secondary loading of molecular sieve: The molecular sieve after primary loading is placed in 10 mL of dimethylaminodimethylsilane solution for ultrasonic loading. The ultrasonic loading temperature is 60℃ and the ultrasonic time is 30 min. After filtration and drying, the molecular sieve adsorbent is prepared.

[0087] CO2 adsorption:

[0088] The fixed-bed reactor contains a glass adsorption column, the temperature of which is controlled by a heating furnace. During adsorption, 10 g of molecular sieve adsorbent is packed into the adsorption column, and a dry CO2 / N2 mixture (CO2 content 12.5 wt%) is passed through the pipeline at a flow rate of 40 mL / min. The CO2 content at the inlet and outlet is measured by gas chromatography. The CO2 adsorption capacity is 2.6 mmol / g.

[0089] Comparative Example 3:

[0090] Preparation of molecular sieve adsorbents:

[0091] (1) Pretreatment: Take 10g of ZSM-5 molecular sieve, add 50mL of 20% nitric acid, stir with a magnetic stirrer for 0.5h, wash with distilled water until neutral, filter and dry;

[0092] (2) Modified molecular sieve: Add 100 mL of 30% H2O2 and stir at 20℃ for 2 h, then impregnate for 20 h, wash until neutral, and dry at 150℃;

[0093] (3) First loading of molecular sieve: Adjust the microwave power to 800W, put the modified molecular sieve into 20mL of monoethanolamine solution, stir with a magnetic stirrer for 10min, let stand for 4h, add another 10mL of monoethanolamine solution, stir with a magnetic stirrer for 10min, let stand for 4h, stop microwave induction, filter and dry.

[0094] (4) Secondary loaded molecular sieve: The molecular sieve after primary loading is immersed in 10 mL of bis(dimethylaminodimethylsilane) solution for loading, filtered and dried to prepare the molecular sieve adsorbent.

[0095] CO2 adsorption:

[0096] The fixed-bed reactor contains a glass adsorption column, the temperature of which is controlled by a heating furnace. During adsorption, 10 g of molecular sieve adsorbent is packed into the adsorption column, and a dry CO2 / N2 mixture (CO2 content 12.5 wt%) is passed through the pipeline at a flow rate of 40 mL / min. The CO2 content at the inlet and outlet is measured by gas chromatography. The CO2 adsorption capacity is 3.0 mmol / g.

[0097] Comparative Example 4:

[0098] Preparation of molecular sieve adsorbents:

[0099] (1) Pretreatment: Take 10g of ZSM-5 molecular sieve, add 50mL of 20% nitric acid, stir with a magnetic stirrer for 0.5h, wash with distilled water until neutral, filter and dry;

[0100] (2) Modified molecular sieve: Add 100 mL of 30% H2O2 and stir at 20℃ for 2 h, then impregnate for 20 h, wash until neutral, and dry at 150℃;

[0101] (3) First loading of molecular sieve: The modified molecular sieve was placed in 20 mL of monoethanolamine solution, stirred with a magnetic stirrer for 10 min, and then allowed to stand for 4 h. Another 10 mL of monoethanolamine solution was added, and the mixture was stirred with a magnetic stirrer for 10 min. After standing for 4 h, microwave induction was stopped, and the mixture was filtered and dried.

[0102] (4) Secondary loading of molecular sieve: The molecular sieve after primary loading is placed in 10 mL of dimethylaminodimethylsilane solution for ultrasonic loading. The ultrasonic loading temperature is 60℃ and the ultrasonic time is 30 min. After filtration and drying, the molecular sieve adsorbent is prepared.

[0103] CO2 adsorption:

[0104] The fixed-bed reactor contains a glass adsorption column, the temperature of which is controlled by a heating furnace. During adsorption, 10 g of molecular sieve adsorbent is packed into the adsorption column, and a dry CO2 / N2 mixture (CO2 content 12.5 wt%) is passed through the pipeline at a flow rate of 40 mL / min. The CO2 content at the inlet and outlet is measured by gas chromatography. The CO2 adsorption capacity is 3.4 mmol / g.

[0105] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

[0106] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for preparing a molecular sieve adsorbent, characterized in that, After pretreatment, pore modification, primary loading, and secondary loading of the molecular sieve support, a molecular sieve adsorbent is obtained. The specific preparation steps are as follows: (1) Pretreatment: The molecular sieve carrier is acid washed with a mass ratio of molecular sieve carrier to acid of 1:0.5-1:

10. After stirring for 0.5h-3h, it is washed with distilled water until neutral, filtered, and dried. (2) Modified molecular sieve: The pretreated molecular sieve is modified by changing the pore size and modifying the internal pores. It is modified by a modifier. The treatment temperature is 5℃-100℃, the treatment time is 0.5 h-8 h, the immersion time is 0.5 h-24 h, the modified sieve is washed until neutral, filtered, and dried. The modifier is one of hydrogen peroxide, phosphoric acid, sodium hypochlorite, perchloric acid, sodium hydroxide, and potassium hydroxide. (3) First loading of molecular sieve: Under microwave induction, the modified molecular sieve is loaded with amine solution, stirred and allowed to stand for 0.5 h-8 h; the same type of amine solution is added again for loading, stirred and allowed to stand for the same time, microwave induction is stopped, filtered and dried. (4) Secondary loaded molecular sieve: The molecular sieve after primary loading is ultrasonically loaded with aminosilane solvent, filtered and dried to prepare molecular sieve adsorbent.

2. The preparation method according to claim 1, characterized in that... The acids mentioned in step (1) include nitric acid, sulfuric acid, and hydrochloric acid.

3. The preparation method according to claim 1, characterized in that... The molecular sieve is of type MCM-41, ZSM-5, SAPO-34, MOR, or NaY.

4. The preparation method according to claim 1, characterized in that... The microwave power mentioned in step (3) is 600~800W, and the microwave radiation time is 5-10 min.

5. The preparation method according to claim 1, characterized in that... The amine solution mentioned in step (3) is at least one of monoethanolamine, diethanolamine, diethylenetriamine, triethanolamine, diisopropanolamine, 2-aminoisobutanol, N-methylmonoethanolamine, and N-methyldiethanolamine.

6. The preparation method according to claim 1, characterized in that... The aminosilane mentioned in step (4) is one of bis(dimethylaminodimethylsilane) or aminopropyltriethoxysilane.

7. The preparation method according to claim 1, characterized in that... In step (4), the ultrasonic dispersion loading time is 30 min-60 min, and the ultrasonic dispersion loading temperature is 50℃-80℃.

8. The application of the molecular sieve adsorbent prepared by the method according to claim 1 in the adsorption of CO2 gas, characterized in that... CO2 is adsorbed using a fixed-bed reactor containing a glass adsorption column.