Adsorbent for directly capturing CO2 from air as well as preparation method and application of adsorbent
By performing crystallization and ion exchange on zeolite molecular sieves, an adsorbent with strong adsorption properties is formed, which solves the problem of low CO2 capture efficiency in existing technologies and achieves efficient and low-cost CO2 capture.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-01-12
- Publication Date
- 2026-03-10
AI Technical Summary
Existing adsorption materials have poor affinity and adsorption capacity for ultra-low concentrations of CO2 when directly capturing CO2 from the air, resulting in low capture efficiency and high cost. Amine-functionalized materials suffer from oxidation deactivation and high regeneration energy consumption.
Zeolite molecular sieves are mixed with alkali metal reagents to carry out a crystallization reaction to form a chalcogenide precursor. Then, it undergoes ion exchange with barium or strontium salt solutions to form an adsorbent with strong adsorption properties. The high charge and large ionic radius of barium or strontium ions occupy six-membered ring sites in the chalcogenide framework, enhancing the adsorption of CO2. Regeneration is achieved through physical adsorption.
It provides excellent adsorption performance at low CO2 concentrations, with an adsorption capacity of up to 1.76 mmol/g, which improves the capture efficiency, reduces regeneration energy consumption, and is suitable for large-scale industrial production.
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Figure CN121623742A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The application belongs to the technical field of carbon capture, and particularly relates to a sorbent for direct air capture of CO2 and a preparation method and application thereof. BACKGROUND
[0002] With the increasingly serious global climate change problem, developing negative emission technology has become a key way to achieve the temperature control target. Direct air capture (DAC) technology can directly capture carbon dioxide from the atmosphere, thereby reducing the concentration of carbon dioxide in the atmosphere, and is one of the key technologies to achieve the temperature control target. However, the large-scale application of this technology still faces the following problems: the existing adsorption materials have poor affinity and adsorption capacity for ultra-low concentration CO2, resulting in low capture efficiency of the direct air capture device and high capture cost.
[0003] At present, the adsorption materials used in DAC technology mainly include amine functionalized porous materials and physical adsorbents (such as zeolites, activated carbon, metal organic framework materials, etc.). However, amine functionalized materials often face problems such as oxidation and deactivation of amine groups, high regeneration energy consumption, and insufficient cycle stability in practical application. Traditional physical adsorbents such as the commonly used 13X zeolite have good adsorption performance under high concentration CO2 conditions, but under low concentration CO2 conditions, due to the weak adsorption of the pore structure and cation sites to CO2, the adsorption capacity is significantly reduced, which is difficult to meet the requirements of practical application. SUMMARY
[0004] In view of the problems existing in the prior art, the purpose of the present application is to provide a sorbent for direct air capture of CO2 and a preparation method and application thereof, which exhibits good adsorption performance for low concentration CO2, and the preparation method has mild process conditions, simple steps, and readily available raw materials, and has good application prospect.
[0005] The first aspect of the present application provides a method for preparing a sorbent for direct air capture of CO2, comprising the following steps: S1, mixing a zeolite molecular sieve with an alkali reagent to perform a crystal transformation reaction to obtain a precursor; S2, mixing the precursor with a metal salt solution to perform ion exchange to obtain the sorbent; The metal salt solution comprises at least one of a barium salt solution and a strontium salt solution.
[0006] The application can convert zeolite molecular sieve into precursor (chabazite) by mixing zeolite molecular sieve with alkali reagent for crystal transformation reaction, and then ion exchange reaction is carried out between the precursor and metal salt solution to replace alkali metal ions with barium ions or strontium ions, and after filtration, washing and drying treatment, the adsorbent for direct air capture is obtained. The inventors found that the performance of the obtained adsorbent is better when barium salt and / or strontium salt is used for ion exchange, because strontium ions and barium ions can provide moderate high charge, which can form a strong local electric field to enhance the action of zeolite on CO2 molecules. In addition, strontium ions and barium ions have a large ion radius, so they tend to occupy the position near the six-membered ring in the cage rather than the eight-membered ring in the chabazite (CHA) framework, thereby playing a strong adsorption role while avoiding the problem of cation blockage of the pore to increase the gas diffusion resistance. In addition, the action of strontium ions and barium ions as main group metal ions on CO2 is mainly reversible physical adsorption, which ensures that the adsorbent can be efficiently regenerated under mild conditions to meet the cycle operation requirements of DAC technology.
[0007] In some embodiments, the zeolite molecular sieve comprises at least one of HY type zeolite and Y type zeolite.
[0008] In some preferred embodiments, the zeolite molecular sieve is HY type zeolite.
[0009] In some embodiments, the zeolite molecular sieve has a silicon-aluminum ratio of 2-3. For example, the silicon-aluminum ratio of the zeolite molecular sieve can be, but is not limited to, 2, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.6, 2.8, 2.9, 3 or other values within the range. The silicon-aluminum ratio refers to the molar ratio of silicon to aluminum in the zeolite molecular sieve, which can be determined by, for example, inductively coupled plasma spectroscopy (ICP) and X-ray fluorescence spectroscopy (XRF) tests.
[0010] In some preferred embodiments, the zeolite molecular sieve has a silicon-aluminum ratio of 2.5-2.7.
[0011] The silicon-aluminum ratio of the zeolite molecular sieve is within the above range, and the adsorption performance of the obtained adsorbent is better.
[0012] In some embodiments, the alkali reagent comprises potassium hydroxide (KOH).
[0013] In some embodiments, the metal salt comprises at least one of BaCl2, Ba(NO3)2, SrCl2 and Sr(NO3)2.
[0014] In some preferred embodiments, the metal salt comprises at least one of BaCl2 and SrCl2.
[0015] In some more preferred embodiments, the metal salt is BaCl2.
[0016] In some embodiments, the metal salt solution is an aqueous solution of the metal salt.
[0017] In some embodiments, the concentration of the alkali metal agent is 0.5-1.5 mol / L. The concentration of the alkali metal agent may, for example, be but is not limited to 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L, 1.0 mol / L, 1.1 mol / L, 1.2 mol / L, 1.3 mol / L, 1.4 mol / L, 1.5 mol / L, or other values within the range.
[0018] In some embodiments, the mass-volume ratio of the zeolite molecular sieve to the alkali metal agent is 1 g:(5-15) mL.
[0019] In some embodiments, the temperature of the crystallization conversion reaction is 85-105°C. The temperature of the crystallization conversion reaction may, for example, be but is not limited to 85°C, 86°C, 87°C, 88°C, 89°C, 90°C, 91°C, 92°C, 93°C, 94°C, 95°C, 96°C, 97°C, 98°C, 99°C, 100°C, 101°C, 102°C, 103°C, 104°C, 105°C, or other values within the range.
[0020] In some embodiments, the time of the crystallization conversion reaction is 72-120 h. The time of the crystallization conversion reaction may, for example, be but is not limited to 72 h, 74 h, 76 h, 78 h, 80 h, 82 h, 84 h, 86 h, 88 h, 90 h, 92 h, 94 h, 96 h, 98 h, 100 h, 102 h, 104 h, 106 h, 108 h, 110 h, 112 h, 114 h, 116 h, 118 h, 120 h, or other values within the range.
[0021] In some embodiments, a filtration, washing, and drying process is performed after the crystallization conversion reaction.
[0022] In some embodiments, the concentration of the metal salt solution is 0.5-1.5 mol / L. The concentration of the metal salt solution may, for example, be but is not limited to 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L, 1.0 mol / L, 1.1 mol / L, 1.2 mol / L, 1.3 mol / L, 1.4 mol / L, 1.5 mol / L, or other values within the range.
[0023] In some embodiments, the mass volume ratio of the precursor to the metal salt solution is 1 g: (20~80) mL.
[0024] In some embodiments, the temperature of the ion exchange is 70~90℃. The temperature of the ion exchange may, for example, be but is not limited to 70℃, 71℃, 72℃, 73℃, 74℃, 75℃, 76℃, 77℃, 78℃, 79℃, 80℃, 81℃, 82℃, 83℃, 84℃, 85℃, 86℃, 87℃, 88℃, 89℃, 90℃, or other values within the range.
[0025] In some embodiments, the time of the ion exchange is 8~16 h. The time of the ion exchange may, for example, be but is not limited to 8 h, 9 h, 10 h, 11 h, 12 h, 13 h, 14 h, 15 h, 16 h, or other values within the range.
[0026] In some embodiments, the number of times of the ion exchange is 1~5 times.
[0027] In some preferred embodiments, the number of times of the ion exchange is 2~4 times.
[0028] In some more preferred embodiments, the number of times of the ion exchange is 3 times.
[0029] In some embodiments, the ion exchange is followed by a filtration, washing, and drying process.
[0030] The second aspect of the present application provides an adsorbent for direct air capture of CO2, prepared by the method described above.
[0031] In some embodiments, the adsorbent is subjected to an activation process before use.
[0032] In some embodiments, the activation temperature is 300~500℃.
[0033] In some embodiments, the activation time is 6~12 h.
[0034] In some embodiments, the adsorbent for direct air capture of CO2 has a silica-to-alumina ratio of 2~3.
[0035] In some preferred embodiments, the adsorbent for direct air capture of CO2 has a silica-to-alumina ratio of 2.1~2.3.
[0036] In some more preferred embodiments, the adsorbent for direct air capture of CO2 has a silica-to-alumina ratio of 2.2.
[0037] The third aspect of the present application provides a direct air capture device comprising the above-mentioned adsorbent for direct air capture of CO2 Compared with the prior art, the present application has the following beneficial effects: (1) The adsorbent for direct air capture of CO2 provided by the present application has an adsorption capacity for CO2 ≥ 1 mmol / g, which can be as high as 1.76 mmol / g, at a low concentration of CO2 (400 ppm), showing excellent adsorption performance for low-concentration CO2, and can effectively improve the capture efficiency of a direct air capture (DAC) device.
[0038] (2) The preparation method provided by the present application uses zeolite molecular sieve as a raw material, and is prepared by hydrothermal crystal transformation and ion exchange process, which has mild reaction conditions, simple steps, reliable route, and readily available raw materials, and has the potential for large-scale industrial production.
[0039] (3) The adsorbent for direct air capture of CO2 provided by the present application is based on physical adsorption, and the energy consumption required for desorption and regeneration is significantly lower than that of amine-based chemical adsorbent, and usually only requires mild heating or small pressure reduction. BRIEF DESCRIPTION OF DRAWINGS
[0040] Figure 1 XRD pattern of the adsorbent obtained in Examples 1-2.
[0041] Figure 2 Thermogravimetric pattern of the adsorbent obtained in Example 1.
[0042] Figure 3 CO2 isothermal pressure swing adsorption test graph of the adsorbent obtained in Examples 1-2 and Comparative Examples 1-7 at 25℃.
[0043] Figure 4 Breakthrough graph of the adsorbent obtained in Examples 1-2 and Comparative Example 1 in a simulated air environment at 25℃. DETAILED DESCRIPTION
[0044] The content of the present application will be further described in detail through specific examples, and the specific examples do not represent a limitation on the protection scope of the present application. Some non-essential modifications and adjustments made by others according to the concept of the present application still fall within the protection scope of the present application. The raw materials, reagents or devices used in the examples can be obtained from conventional commercial channels, or can be obtained by existing technical methods. Unless otherwise specified, the test or test method is a conventional method in the art.
[0045] HY type zeolite with a silicon-aluminum ratio of 2.6, purchased from Sinopec Catalyst Co., Ltd. Qilu Branch.
[0046] Example 1 The method for preparing the adsorbent for directly capturing CO2 from air provided in the embodiment comprises the following steps: S1, crystal transformation reaction: 1.8 g of HY type zeolite (silicon-aluminum ratio of 2.6) is mixed with 15 mL of KOH aqueous solution (concentration of 1 mol / L), and then stirred uniformly and transferred into a polytetrafluoroethylene-lined high-pressure reaction kettle, the reaction kettle is placed in a homogeneous reactor at 95℃ for reaction for 96 h, after the reaction is completed, the reaction kettle is naturally cooled to room temperature, and then filtered, washed with deionized water, and dried at 80℃ for 12 h to obtain a precursor.
[0047] S2, ion exchange: 5 g of the precursor is added into 300 mL of BaCl2 aqueous solution (concentration of 1 mol / L), and stirred at 90℃ for 12 h under water bath condition, and the ion exchange is repeated twice, that is, the ion exchange is performed for three times. After the ion exchange is completed, the product is filtered, washed with deionized water, and dried at 80℃ for 12 h to obtain the adsorbent for directly capturing CO2 from air.
[0048] The adsorbent obtained in Example 1 is subjected to XRD analysis, and the results are shown in Figure 1 It can be seen that the obtained adsorbent shows typical crystal structure characteristics of chabazite.
[0049] The adsorbent obtained in Example 1 is subjected to thermogravimetric analysis, and the results are shown in Figure 2 It can be seen that the obtained adsorbent has good thermal stability.
[0050] The silicon-aluminum ratio of the adsorbent obtained in Example 1 is measured by X-ray fluorescence spectrum (XRF), and the silicon-aluminum ratio is 2.2.
[0051] Example 2 The method for preparing the adsorbent for directly capturing CO2 from air provided in the embodiment comprises the following steps: S1, crystal transformation reaction: 1.8 g of HY type zeolite (silicon-aluminum ratio of 2.6) is mixed with 15 mL of KOH aqueous solution (concentration of 1 mol / L), and then stirred uniformly and transferred into a polytetrafluoroethylene-lined high-pressure reaction kettle, the reaction kettle is placed in a homogeneous reactor at 95℃ for reaction for 96 h, after the reaction is completed, the reaction kettle is naturally cooled to room temperature, and then filtered, washed with deionized water, and dried at 80℃ for 12 h to obtain a precursor.
[0052] S2, ion exchange: 5 g of the precursor is added into 300 mL of BaCl2 aqueous solution (concentration of 1 mol / L), and stirred at 90℃ for 12 h under water bath condition, and the ion exchange is repeated twice, that is, the ion exchange is performed for three times. After the ion exchange is completed, the product is filtered, washed with deionized water, and dried at 80℃ for 12 h to obtain the adsorbent for directly capturing CO2 from air.
[0053] The adsorbent for capturing CO2 from direct air obtained in Example 2 was subjected to XRD analysis, and the results are shown in FIG. 2. It can be seen that the adsorbent shows typical crystal structure characteristics of chabazite. Figure 1
[0054] The adsorbent obtained in Example 2 was subjected to X-ray fluorescence spectroscopy (XRF) to measure the silicon-aluminum ratio, and the result was 2.2.
[0055] Comparative Example 1 The adsorbent used in this comparative example was a commercially available 13X zeolite molecular sieve, which was purchased from Luoyang Jianlong Micro-nano New Material Co., Ltd.
[0056] Comparative Example 2 The difference between this comparative example and Example 1 is only that no ion exchange reaction is performed, and the specific steps include the following: 1.8 g of HY type zeolite (silicon-aluminum ratio of 2.6) is mixed with 15 mL of KOH aqueous solution (concentration of 1 mol / L), stirred uniformly, and then transferred into a polytetrafluoroethylene-lined high-pressure reaction kettle, and the reaction kettle is placed in a homogeneous reactor at 95°C for 96 h. After the reaction is completed, it is naturally cooled to room temperature, and after being filtered and washed with deionized water, it is dried at 80°C for 12 h to obtain an adsorbent.
[0057] Comparative Example 3 The difference between this comparative example and Example 1 is only that the metal salt solution in step S2 is replaced by an aqueous MgCl2 solution instead of an aqueous BaCl2 solution.
[0058] Comparative Example 4 The difference between this comparative example and Example 1 is only that the metal salt solution in step S2 is replaced by an aqueous CaCl2 solution instead of an aqueous BaCl2 solution.
[0059] Comparative Example 5 The difference between this comparative example and Example 1 is only that the metal salt solution in step S2 is replaced by an aqueous LiCl solution instead of an aqueous BaCl2 solution.
[0060] Comparative Example 6 The difference between this comparative example and Example 1 is only that the metal salt solution in step S2 is replaced by an aqueous NaCl solution instead of an aqueous BaCl2 solution.
[0061] Comparative Example 7 The difference between this comparative example and Example 1 is only that the metal salt solution in step S2 is replaced by an aqueous CsCl solution instead of an aqueous BaCl2 solution.
[0062] In order to verify the performance of the adsorbent for capturing CO2 from direct air obtained by the present application, the adsorbents obtained in each example and comparative example were subjected to the following performance tests, and the specific steps are as follows: (1) Single-component performance test: using a Mic3FLEX type physical adsorber, the adsorbents obtained in Examples 1-2 and Comparative Examples 1-7 were activated at 300°C under vacuum for 10 h, and after the temperature dropped to room temperature, isothermal pressure swing adsorption test of high-purity CO2 (99.999%) was carried out, the adsorption temperature was 25°C, and the results are shown in Figure 3 , the CO2 adsorption amount at 400 ppm was recorded, and the results are shown in Table 1.
[0063] Table 1 The results show that the adsorbent for directly capturing CO2 from air provided by the present application has a CO2 adsorption capacity of ≥1 mmol / g at low concentration CO2 (400 ppm), which can be as high as 1.76 mmol / g, showing excellent adsorption performance for low concentration CO2, and can effectively improve the capture efficiency of the DAC device. As can be seen from Examples 1 and Comparative Example 1, the adsorbent provided by the present application is better than 13X zeolite molecular sieve. As can be seen from Examples 1 and Comparative Examples 3-4, magnesium ions and calcium ions have a limited range of electrostatic field effect due to their small ionic radius, which cannot effectively cover the space in the channel and adsorb CO2. As can be seen from Examples 1 and Comparative Examples 2, 5-7, monovalent metal ions tend to preferentially occupy octagonal rings, resulting in cation blockage of the channel, which affects the adsorption capacity, while barium ions and strontium ions tend to occupy sites near the six-membered ring in the cage rather than the octagonal ring, and can form a stronger local electric field, making them have better CO2 capture capacity, allowing them to play a strong adsorption role while avoiding the problem of increased gas diffusion resistance caused by cation blockage of the channel.
[0064] (2) Multi-component performance test: the adsorbents obtained in Examples 1-2 and Comparative Example 1 were activated at 300°C under vacuum for 10 h, and after the temperature dropped to room temperature, the adsorbents were filled into a quartz fixed bed adsorption column, and air simulation gas (400 ppm CO2, 400 ppm Ar, 21% O2, and the balance being N2) was introduced into the inlet of the adsorption column, the gas flow rate was 50 mL / min, and the test temperature was 25°C. The CO2 in the outlet gas was detected by gas chromatography and the breakthrough curve was drawn, and the results are shown in Figure 4 .
[0065] The results show that the adsorbents obtained in Examples 1-2 have not detected CO2 in the outlet gas for a long time in the dynamic adsorption test, and breakthrough occurs only when the adsorbent is close to saturation, which indicates that the adsorbent has excellent dynamic adsorption performance for CO2 and can achieve complete adsorption of CO2 for a long time. The CO2 dynamic adsorption capacity of the adsorbent was calculated by the following formula: In the formula, q is the adsorption amount, t is the time, C is the concentration, and m is the sample mass.
[0066] The calculated CO2 dynamic adsorption capacity of the adsorbent obtained in Example 1 is 1.12 mmol / g, and the calculated CO2 dynamic adsorption capacity of the adsorbent obtained in Example 2 is 0.67 mmol / g, which is significantly better than 0.37 mmol / g of Comparative Example 1.
[0067] The results show that the adsorbent for directly capturing CO2 from air provided by the application exhibits excellent adsorption performance for low-concentration CO2, and can effectively improve the capture efficiency of a direct air capture (DAC) device when applied to the DAC device, and the preparation method has mild process conditions, simple steps, and readily available raw materials, and has good application prospects.
[0068] The above examples are only used to illustrate the technical solutions of the application and not to limit the protection scope of the application, and although the application has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that the technical solutions of the application can be modified or replaced by equivalents without departing from the essence and scope of the technical solutions of the application.
Claims
1. A method of preparing a sorbent for direct air capture of CO2, characterized in that, The method comprises the following steps: S1, mixing a zeolite molecular sieve with an alkali reagent to perform a crystal transformation reaction to obtain a precursor; S2, mixing the precursor with a metal salt solution to perform ion exchange to obtain the adsorbent; The metal salt solution comprises at least one of a barium salt solution and a strontium salt solution.
2. The method of claim 1, wherein, The zeolite molecular sieve comprises at least one of a HY type zeolite and a Y type zeolite.
3. The method of claim 1, wherein, The zeolite molecular sieve has a silicon-aluminum ratio of 2-3.
4. The method of claim 1, wherein, The alkali reagent comprises KOH.
5. The method of claim 1, wherein, The metal salt comprises at least one of BaCl2, Ba(NO3)2, SrCl2 and Sr(NO3)2.
6. The method of claim 1, wherein, The step S1 satisfies at least one of the following characteristics (1)-(5): (1) the concentration of the alkali reagent is 0.5-1.5 mol / L; (2) the mass-volume ratio of the zeolite molecular sieve to the alkali reagent is 1g:(5-15)mL; (3) the temperature of the crystal transformation reaction is 85-105℃; (4) the time of the crystal transformation reaction is 72-120 h; (5) filtration, washing and drying treatment are performed after the crystal transformation reaction.
7. The method of claim 1, wherein, The step S2 satisfies at least one of the following characteristics (1)-(6): (1) the concentration of the metal salt solution is 0.5-1.5 mol / L; (2) the mass-volume ratio of the precursor to the metal salt solution is 1g:(20-80)mL; (3) the temperature of the ion exchange is 70-90℃; (4) the time of the ion exchange is 8-16 h; (5) the number of times of the ion exchange is 1-5; (6) filtration, washing and drying treatment are performed after the ion exchange.
8. A sorbent for direct air capture of CO2, characterized in that, The adsorbent for directly capturing CO2 from air is prepared by the method according to any one of claims 1-7.
9. The adsorbent of claim 8, wherein, The adsorbent for directly capturing CO2 from air satisfies at least one of the following characteristics (1)-(4): (1) the adsorbent is activated before use; (2) the adsorbent is activated before use, and the activation temperature is 300-500℃; (3) the adsorbent is activated before use, and the activation time is 6-12 h; (4) the adsorbent has a silicon-aluminum ratio of 2-3.
10. A direct air capture device, characterized by, The adsorbent for directly capturing CO2 from air comprises the adsorbent according to any one of claims 8-9.