Hydrophobically and aminogroup modified molecular sieve, preparation method thereof and application of the molecular sieve in capturing low-concentration carbon dioxide in air

Abstract

This invention discloses a molecular sieve that is simultaneously modified by hydrophobication and amination, its preparation method, and its application in capturing low-concentration carbon dioxide from the air. The preparation method of the simultaneously modified molecular sieve includes: mixing a macroporous molecular sieve with a solvent; mixing the mixture of the macroporous molecular sieve and solvent with a silanizing agent and an amination agent; stirring and reacting; and washing and drying after the reaction to obtain the simultaneously modified molecular sieve. This invention uses a macroporous molecular sieve and applies surface alkylation modification. An alkyl coupling agent condenses with the hydroxyl groups (Si-OH) on the molecular sieve surface, and then an amination group is introduced to increase the carbon dioxide adsorption capacity. Based on a macroporous molecular sieve with a high CO2 adsorption capacity, this invention further improves its water resistance and adsorption capacity, and has strong practical application value.

Description

Technical Field

[0001] This invention relates to a molecular sieve that is simultaneously modified by hydrophobication and amination, its preparation method, and its application in capturing low-concentration carbon dioxide from the air. Background Technology

[0002] Traditional methods for reducing carbon dioxide emissions mainly include chemical absorption and physical adsorption, but these methods suffer from problems such as low adsorption efficiency and high energy consumption.

[0003] Molecular sieves are excellent adsorbents, exhibiting selective adsorption capabilities for molecules with varying shapes, diameters, polarities, and degrees of unsaturation. Compared to traditional adsorption methods, they offer advantages such as high selectivity, high adsorption capacity, environmental friendliness, convenient regeneration, and low operating costs. One method to improve the adsorption performance of molecular sieves is amination modification, where amine groups are introduced onto the surface or pores of the molecular sieve, reacting with carbon dioxide to form carbamates or bicarbonates. US Patent US8574340B2 discloses a method for adsorbing carbon dioxide by grafting an amination reagent, using 3-aminopropyltriethoxysilane grafted onto MCM-41, achieving a carbon dioxide adsorption capacity of 1.8 mmol / g at 25°C and 1 bar. Patent CN102553552B loads PEI onto SBA-15 mesoporous molecular sieves with an amine loading of 40 wt%, achieving a carbon dioxide adsorption capacity of 3.2 mmol / g at 75°C and 1 bar.

[0004] However, in high humidity environments, the adsorption performance of molecular sieves decreases significantly. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention provides a technology for simultaneously modifying macroporous molecular sieves through hydrophobication and amination, and for capturing low-concentration carbon dioxide from the air.

[0006] This invention provides the following technical solutions: A method for preparing a molecular sieve that is simultaneously modified by hydrophobicity and amination includes the following steps: Step 1: Mix the macroporous molecular sieve with the solvent; Step 2: The mixture of macroporous molecular sieve and solvent is mixed with silanizing and amination reagents, stirred and reacted. After the reaction is completed, the mixture is washed and dried to obtain the molecular sieve that is simultaneously modified by hydrophobication and amination.

[0007] Furthermore, the macroporous molecular sieve includes one or more of NaX molecular sieve, NaY molecular sieve, Na-MOR molecular sieve, and Na-Beta molecular sieve.

[0008] Furthermore, the solvent includes one or more of toluene, methanol, ethanol, acetonitrile, tetrahydrofuran, acetone, dichloromethane, trichloromethane, dichloroethane, xylene, and chlorobenzene; the solid-liquid ratio of the macroporous molecular sieve to the solvent is 1g:5-15mL.

[0009] Furthermore, the silanizing agent includes one or more of the following: triethoxysilane, trimethoxysilane, methyldiethoxysilane, methyltrichlorosilane, phenyltriethoxysilane, tetraethoxysilane, γ-aminopropyltriethoxysilane, vinyltriethoxysilane, and methyltriethoxysilane. The mass ratio of macroporous molecular sieve to silanizing reagent is 1:0.2-0.6, preferably 1:0.3-0.4.

[0010] Further, the amination reagent includes one or more of methylamine, ethylamine, propylamine, isopropylamine, butylamine, dimethylamine, diethylamine, triethylamine, aniline, and p-toluidine; the mass ratio of macroporous molecular sieve to amination reagent is 1:0.1-0.4, preferably 1:0.2-0.3.

[0011] The present invention also discloses the application of the aforementioned hydrophobic and amination-modified molecular sieve in capturing low-concentration carbon dioxide from the air.

[0012] The molecular sieve described in this invention is tested at temperatures between 20°C and 80°C, such as 20°C, 30°C, 50°C, 70°C, and 80°C.

[0013] Compared with existing technologies, the beneficial effects of this invention are as follows: This invention uses macroporous molecular sieves, modifies them through surface alkylation, condenses alkyl coupling agents with hydroxyl groups (Si-OH) on the molecular sieve surface, and then introduces amine groups for modification to increase carbon dioxide adsorption capacity. Based on macroporous molecular sieves with high CO2 adsorption capacity, this invention further improves their water resistance and adsorption capacity, and has strong practical application value. Detailed Implementation

[0014] The present invention will be further described below with reference to specific embodiments, but the scope of protection of the present invention is not limited thereto.

[0015] Carbon dioxide adsorption efficiency test method: Outdoor air was pumped into a flow meter to control the airflow rate. Since this study aimed to perform hydrophobic modification to successfully add hydrophobic groups to the adsorbent material, two methods were used. One method involved passing the air through concentrated sulfuric acid to remove as much moisture as possible, testing the CO2 adsorption efficiency of the modified sample under dry conditions. The other method involved passing the air through a container filled with deionized water to saturate it with water vapor, then passing the air through the adsorbent sample to test its CO2 adsorption capacity under saturated water vapor conditions. The air containing the adsorbed sample was then introduced into a portable infrared CO2 analyzer, and the CO2 concentration C at the air outlet was recorded in real time. t Before testing, turn on the instrument's internal air filtration system to ensure the internal CO2 concentration matches the external concentration. At this point, the instrument displays the equilibrium concentration C0. During testing, as the sample adsorbs CO2 from the air, the recorded CO2 value gradually decreases. After a period of time, the recorded value returns to the equilibrium concentration, at which point the test is complete. Use Origin to analyze the C0 concentration. t By plotting / C0 with respect to time t, the breakthrough curve of CO2 adsorption by the adsorbent can be obtained. Through the breakthrough curve, information such as adsorbent dosage, adsorption capacity, adsorption rate, capture effect, and activation conditions can be judged.

[0016] Example 1: Molecular sieve modification (triethoxysilane and ethylamine): 50 ml of anhydrous toluene and 5 g of NaX molecular sieve were added to a dry beaker. After ultrasonic dispersion for 10 min, 2 g of triethoxysilane was added and mixed thoroughly. Then, 1 g of ethylamine was added and stirred for 6 h. The mixture was washed with ethanol, centrifuged, and dried in an oven at 100 °C. The NaX molecular sieve was produced by Nankai University and had a particle size of 30-40 mesh.

[0017] Example 2: The molecular sieve modification method described in Example 2 differs from that in Example 1 in that the silanizing agent is trimethoxysilane of equal mass instead of triethoxysilane in Example 1. Example 3 differs from Example 1 in that the molecular sieve modification method described in Example 3 uses the same mass of methyldiethoxysilane instead of triethoxysilane in Example 1 as the silanizing agent, and uses the same mass of Na-MOR as the molecular sieve. The Na-MOR molecular sieve was produced by Nankai University and has a particle size of 30-40 mesh.

[0018] Example 4: The molecular sieve modification method described in Example 4 differs from that in Example 3 in that the solvent used is methanol of the same volume, and the silanizing agent is tetraethoxysilane of the same mass instead of triethoxysilane in Example 3.

[0019] Example 5 differs from Example 1 in that the solvent used is methanol of the same volume, the silanizing agent is γ-aminopropyltriethoxysilane of the same mass instead of triethoxysilane in Example 1, the molecular sieve is NaY of the same mass, and the amination agent is propylamine of the same mass. The NaY molecular sieve was produced by Nankai University and has a particle size of 30-40 mesh.

[0020] Example 6 differs from Example 1 in that the solvent used is methanol of the same volume, the silanizing agent is vinyltriethoxysilane of the same mass instead of triethoxysilane in Example 1, the molecular sieve is NaY of the same mass, and the amination agent is isopropylamine of the same mass. The NaY molecular sieve was produced by Nankai University and has a particle size of 30-40 mesh.

[0021] Example 7 differs from Example 1 in that the solvent used is an equal volume of ethanol, the silanizing agent is an equal mass of methyltriethoxysilane instead of triethoxysilane in Example 1, the molecular sieve is an equal mass of NaBeta, and the amination agent is an equal mass of aniline. The NaBeta molecular sieve was produced by Nankai University and has a particle size of 30-40 mesh.

[0022] Example 8 differs from Example 1 in that the solvent used is the same volume of xylene, the silanizing agent is the same mass of triethoxysilane instead of triethoxysilane in Example 1, the molecular sieve is the same mass of NaBeta, and the amination agent is the same mass of methylamine. The NaBeta molecular sieve was produced by Shanghai Husheng Laboratory Equipment Co., Ltd., with a particle size of 30-40 mesh.

[0023] Example 9 differs from Example 1 in that the solvent used is the same volume of xylene, the silanizing agent is the same mass of trimethoxysilane instead of triethoxysilane in Example 1, the molecular sieve is the same mass of ZSM-5, and the amination agent is the same mass of methylamine. The ZSM-5 molecular sieve was produced by Shanghai Husheng Laboratory Equipment Co., Ltd., with a particle size of 30-40 mesh.

[0024] The molecular sieve modification method described in Comparative Example 1 differs from that in Example 1 in that it does not involve amination modification, i.e., it does not involve the addition of ethylamine.

[0025] The molecular sieve modification method described in Comparative Example 2 differs from that in Comparative Example 1 in that the same mass of trimethoxysilane is used instead of triethoxysilane in Comparative Example 1, the same mass of NaMOR is used for molecular sieve modification, and no amination modification is performed, i.e., no ethylamine is added.

[0026] The molecular sieve modification method described in Comparative Example 3 differs from that in Comparative Example 1 in that the solvent used is an equal volume of ethylbenzene, the molecular sieve uses an equal mass of NaBeta, and no amination modification is performed, i.e., no ethylamine is added.

[0027] The molecular sieve modification method described in Comparative Example 4 differs from that in Example 1 in that the solvent used is an equal volume of chlorobenzene, and no silanization modification is performed, i.e., no triethoxysilane is added.

[0028] The molecular sieve modification method described in Comparative Example 5 differs from that in Comparative Example 4 in that the solvent used is an equal volume of acetone, the molecular sieve uses an equal mass of NaMOR, the amination reagent is an equal mass of aniline, and no silanization modification is performed, i.e., no triethoxysilane is added.

[0029] The molecular sieve modification method described in Comparative Example 6 differs from that in Comparative Example 4 in that the solvent used is an equal volume of tetrahydrofuran, the molecular sieve uses an equal mass of NaBeta, the amination reagent is an equal mass of methylamine, and no silanization modification is performed, i.e., no triethoxysilane is added.

[0030] The molecular sieve modification and carbon dioxide adsorption effect testing methods in the remaining examples and comparative examples are the same as those in Example 1.

[0031] Table 1.1 Adsorption capacity of molecular sieves under humidified flow before and after alkylation-amineation modification .

[0032] Table 1.2 Adsorption capacity of molecular sieves under humidified flow after alkylation or amination modification .

[0033] The modified adsorption capacity in Tables 1.1-1.2 refers to the adsorption capacity of the molecular sieve for CO2 under humid gas flow after it has been modified by one (Comparative Examples 1-6) or two (Examples 1-6) of silanizing and amination reagents.

[0034] The adsorption capacity before modification in Table 1.1 refers to the adsorption capacity of the molecular sieve for CO2 directly under a humid gas flow without modification treatment.

[0035] The contents described in this specification are merely an enumeration of the implementation forms of the inventive concept, and the scope of protection of this invention should not be regarded as limited to the specific forms described in the embodiments.

Claims

1. A method for preparing a molecular sieve simultaneously modified by hydrophobication and amination, characterized in that, Includes the following steps: Step 1: Mix the macroporous molecular sieve with the solvent; Step 2: The mixture of macroporous molecular sieve and solvent is mixed with silanizing and amination reagents, stirred and reacted. After the reaction is completed, the mixture is washed and dried to obtain the molecular sieve that is simultaneously modified by hydrophobication and amination.

2. The preparation method according to claim 1, characterized in that, The macroporous molecular sieve includes one or more of NaX molecular sieve, NaY molecular sieve, Na-MOR molecular sieve, and Na-Beta molecular sieve.

3. The preparation method according to claim 1, characterized in that... The solvent includes one or more of toluene, methanol, ethanol, acetonitrile, tetrahydrofuran, acetone, dichloromethane, trichloromethane, dichloroethane, xylene, and chlorobenzene; the solid-liquid ratio of the macroporous molecular sieve to the solvent is 1g:5-15mL.

4. The preparation method according to claim 1, characterized in that... The silanizing agent includes one or more of the following: triethoxysilane, trimethoxysilane, methyldiethoxysilane, methyltrichlorosilane, phenyltriethoxysilane, tetraethoxysilane, γ-aminopropyltriethoxysilane, vinyltriethoxysilane, and methyltriethoxysilane. The mass ratio of macroporous molecular sieve to silanizing reagent is 1:0.2-0.6, preferably 1:0.3-0.

4.

5. The preparation method according to claim 1, characterized in that... The amination reagent includes one or more of methylamine, ethylamine, propylamine, isopropylamine, butylamine, dimethylamine, diethylamine, triethylamine, aniline, and p-toluidine; the mass ratio of macroporous molecular sieve to amination reagent is 1:0.1-0.4, preferably 1:0.2-0.

3.

6. A molecular sieve that is simultaneously modified by hydrophobication and amination according to any one of claims 1-5.

7. The application of the hydrophobic and amination-modified molecular sieve according to claim 6 in capturing low-concentration carbon dioxide from the air.