Calcium-based adsorbent as well as preparation method and application thereof
By using high-alumina cement and polyvinylpyrrolidone for synergistic modification and pore formation, a calcium-based adsorbent with high mechanical strength and stability was prepared, solving the problem of poor cycle stability of CaO-based adsorbents and achieving a highly efficient CO2 capture effect.
Patent Information
- Application Number
- CN202511395865.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-09-28
- Publication Date
- 2025-12-23
AI Technical Summary
Existing CaO-based adsorbents suffer from poor cycle stability, poor powder flowability, and easy agglomeration. Furthermore, existing preparation processes are complex or time-consuming, making continuous production difficult.
A calcium-based adsorbent was prepared by using calcium hydroxide as the calcium source, high-alumina cement as a modifier, and polyvinylpyrrolidone as a pore-forming agent through steps such as mixing, pressing into strips, drying, and calcination. This process forms a stable Al2O3-CaO structure and interconnected pores, thereby improving mechanical strength and gas diffusion performance.
It significantly improves the mechanical strength and cycle stability of calcium-based adsorbents, enhances gas diffusion performance, meets the needs of industrial CO2 capture, and has a simple and feasible preparation process.
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Figure CN121178112A_ABST
Abstract
Description
Technical Field
[0001] This disclosure belongs to the field of adsorption materials technology, specifically relating to a calcium-based adsorbent, its preparation method, and its application. Background Technology
[0002] With the acceleration of industrialization, carbon dioxide (CO2) emissions are increasing rapidly, and the greenhouse effect is becoming increasingly serious. Existing CO2 capture technologies mainly include chemical absorption, physical adsorption, and membrane separation. Among them, chemical adsorption based on CaO / CaCO3 cycle has advantages such as abundant raw materials, low cost, and large adsorption capacity, but it also has problems such as poor cycle stability, poor powder flowability, and easy agglomeration.
[0003] To improve the mechanical strength and cycle stability of CaO-based adsorbents, the literature often employs chemical impregnation or physical composite methods to combine CaO with porous supports such as SiO2 and Al2O3. However, these methods are complex or result in insufficient dispersibility. Currently, some methods utilize biomass pore-forming to form calcium-based adsorbents, but these require natural air drying and segmented drying, which are time-consuming. Furthermore, the SiO2 in the biomass ash consumes the active CaO, leading to a decrease in the effective adsorbent components. Secondly, hydrothermal synthesis of calcium-based adsorbents is also used. This method requires reactions under high temperature and pressure, resulting in long reaction times, high equipment costs, and limited production capacity, making continuous production difficult. Summary of the Invention
[0004] This disclosure aims to at least solve one of the technical problems existing in the prior art, and to provide a calcium-based adsorbent, its preparation method, and its application.
[0005] In one aspect, this disclosure provides a method for preparing a calcium-based adsorbent, the method comprising:
[0006] Using calcium hydroxide as the calcium source, high-alumina cement as the modifier, and polyvinylpyrrolidone as the pore-forming agent, the raw materials are mixed and deionized water is added to the mixed raw materials. The mixture is stirred to obtain a mud-like solid.
[0007] The mud-like solid is pressed into long strips;
[0008] The strip is dried, calcined, and trimmed to obtain a calcium-based adsorbent.
[0009] Optionally, the mass ratio of the calcium source, the modifying agent, and the pore-forming agent is (220-225):(40-45):(5-6).
[0010] Optionally, the mixing time for each raw material is 8-12 minutes.
[0011] Optionally, 100-150 mL of deionized water may be added to the mixed raw materials, and the stirring time may be 20-40 min.
[0012] Optionally, the diameter of the strip is 4-6 mm.
[0013] Optionally, the temperature for drying the strips is 65-75℃ and the time is 7-9 hours.
[0014] Optionally, the temperature for calcining the strips is 800-900℃ and the time is 0.5-1.5h.
[0015] Optionally, the trimming of long strips includes:
[0016] Use pliers to cut the strip into 8-12mm segments.
[0017] In another aspect of this disclosure, a calcium-based adsorbent is provided, which is prepared using the preparation method described above.
[0018] In another aspect of this disclosure, an application of a calcium-based adsorbent is proposed, which applies the calcium-based adsorbent described above to CO2 adsorption / desorption.
[0019] This disclosure presents a calcium-based adsorbent, its preparation method, and its applications. The preparation method includes: using calcium hydroxide as a calcium source, high-alumina cement as a modifier, and polyvinylpyrrolidone as a pore-forming agent; mixing the raw materials and adding deionized water to the mixture, stirring to obtain a mud-like solid; pressing the mud-like solid into long strips; and drying, calcining, and trimming the strips to obtain the calcium-based adsorbent. This disclosure utilizes high-alumina cement for physical mixing modification, which can form a stable Al2O3-CaO structure during high-temperature calcination, improving mechanical strength and pore structure stability; simultaneously, a suitable pore-forming agent can form interconnected channels during molding and calcination, improving gas diffusion performance. Attached Figure Description
[0020] Figure 1 This is a flowchart illustrating the preparation method of the calcium-based adsorbent according to a specific embodiment of this disclosure.
[0021] Figure 2 This is a schematic diagram illustrating the preparation of the calcium-based adsorbent according to a specific embodiment of this disclosure;
[0022] Figure 3 The CO2 adsorption capacity of the calcium-based adsorbent in Example 1 and the comparative example of this disclosure changes with the number of cycles;
[0023] Figure 4 The adsorption curves of the calcium-based adsorbent in Example 1 and the comparative example of this disclosure after the tenth cycle are shown.
[0024] Figure 5 The adsorption curves of the calcium-based adsorbents in Example 1 and the comparative example of this disclosure after the twentieth cycle are shown. Detailed Implementation
[0025] To enable those skilled in the art to better understand the technical solutions of this disclosure, the disclosure will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain this disclosure and represent a part of the embodiments of this disclosure, not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this disclosure without creative effort are within the protection scope of this disclosure.
[0026] like Figure 1 and Figure 2 As shown, one aspect of this disclosure provides a method for preparing a calcium-based adsorbent, S100, specifically including the following steps S110 to S130:
[0027] S110. Using calcium hydroxide as the calcium source, high-alumina cement as the modifier, and polyvinylpyrrolidone as the pore-forming agent, the raw materials are mixed and deionized water is added to the mixed raw materials. The mixture is stirred to obtain a mud-like solid.
[0028] In some preferred embodiments, the high-alumina cement is CA50-A900. It is important to note that this high-alumina cement has an aluminum content ≥50%, and its main mineral composition is monocalcium aluminate (CA) and monocalcium dialuminate (CA2), with small amounts of dicalcium silicate (C2S) and iron phase. The chemical composition and mineral phase ratio of this cement are strictly standardized, especially the CaO / Al2O3 molar ratio is controlled between 0.8 and 1.0 to ensure the formation of stable calcium aluminate minerals (such as CA6 and CA2) at high temperatures.
[0029] In some other preferred embodiments, the mass ratio of the calcium source, the modifying agent, and the pore-forming agent is (220-225):(40-45):(5-6).
[0030] In this embodiment, PVP acts as a solid pore-forming agent, and its mechanism of action is based on the principle of thermal decomposition and gas phase escape: During the drying stage (70°C), PVP absorbs moisture and swells to form a temporary gel network, maintaining the distance between particles. During the calcination stage (200-400°C), PVP undergoes chain scission, releasing gases such as CO, CO2, and H2O. The gas escape path forms open pores with a pore size of 0.1-5 μm.
[0031] In other preferred embodiments, the mixing time for each raw material is 8-12 minutes, for example, 10 minutes is preferred. The amount of deionized water added to the mixed raw materials is 100-150 mL, and the stirring time is 20-40 minutes, for example, 130 mL, 30 minutes, etc.
[0032] This implementation first involves 10 minutes of dry mechanical mixing to ensure uniform dispersion of nano-sized PVP, and then precisely controlling the amount of water added to form a mud-like substance with ideal rheological properties. Compared to fully wet mixing, this process saves approximately 30% of energy and avoids the problem of uneven early hydration reactions.
[0033] S120. Press the mud-like solid into long strips.
[0034] Specifically, a strip press is used to press the mud-like solid into strips with a diameter of 4-6 mm, for example, preferably 5 mm.
[0035] In this embodiment, a 4-6 mm diameter strip precursor is directly obtained by pressing, eliminating the need for granulation equipment investment. More importantly, PVP decomposition leaves no residue, and the cement mineral phase change directly strengthens the adsorbent skeleton, achieving "zero waste" preparation.
[0036] More importantly, this embodiment innovatively adopts a strip-shaped shearing molding scheme, breaking through the limitations of traditional granules. This helps to increase the bulk density during the compression molding process; for example, a 5mm diameter strip structure achieves a bulk density of 1.2-1.5 g / cm³. 3 Based on this, the reaction vessel can be loaded with 40% more adsorbent, significantly increasing the single-capture capacity.
[0037] It should also be understood that the formed strip structure can facilitate the formation of axial airflow channels. The strip stacking naturally forms 0.5-1mm parallel channels, and the pressure drop is only 1 / 3-1 / 5 of that of a randomly stacked particle bed (measured ΔP = 120Pa / m vs. spherical particle bed > 350Pa / m), which greatly reduces the energy consumption of the blower. The ettringite needle-like crystals formed by cement hydration intertwine to form a network, making the compressive strength of the strip adsorbent > 8MPa, which meets the mechanical wear requirements of fluidized bed circulation.
[0038] S130. The strip is dried, calcined, and trimmed to obtain a calcium-based adsorbent.
[0039] In step S130, the drying temperature of the strip is 65-75°C for 7-9 hours, preferably 70°C for 8 hours. Simultaneously, the calcination temperature of the strip is 800-900°C for 0.5-1.5 hours, preferably 850°C for 1 hour. The strip can then be cut into 8-12mm segments using pliers, preferably 10mm segments.
[0040] In this embodiment, a specific CA50-A900 high-alumina cement is selected for physical mixing modification. During calcination at 850℃, the CA / CA2 in the cement reacts with CaO to form tricalcium aluminate (C50-A900). 12A7) or calcium hexaaluminate (CA6), that is, forming a stable Al2O3-CaO structure with CaO, significantly inhibits CaO grain sintering, improves mechanical strength and pore structure stability, and has better high-temperature resistance than ordinary silicate cement. Furthermore, through the synergistic effect of PVP pore-forming and the high-alumina cement skeleton, interconnected channels can be formed during molding and calcination, improving gas diffusion performance and exhibiting excellent circulation performance. The preparation process is also simple and feasible.
[0041] The method disclosed herein effectively shortens the total time through a one-step process of 30 min mechanical mixing - 8 h pressing - 1 h sintering, and enables large-scale production of adsorbents. Furthermore, the preparation process employs a strip-shaped shearing molding scheme, overcoming the limitations of traditional particles by pressing them into strip structures, increasing packing density, improving single-use capture capacity, and reducing energy consumption.
[0042] In another aspect of this disclosure, a calcium-based adsorbent is provided, characterized in that the calcium-based adsorbent is prepared by the preparation method described above, the specific process of which is described above and will not be repeated here.
[0043] The calcium-based adsorbent disclosed herein has advantages such as good mechanical properties and high cycle stability, and demonstrates performance in 50 CO2 adsorption-desorption cycles to meet the needs of industrial CO2 capture.
[0044] In another aspect of this disclosure, an application of a calcium-based adsorbent is proposed, which applies the calcium-based adsorbent described above to CO2 adsorption / desorption.
[0045] The preparation method of calcium-based adsorbent will be further explained below with reference to specific embodiments:
[0046] Example 1
[0047] S1. Ingredients and Mixing
[0048] Weigh out 222g of calcium hydroxide (Ca(OH)2)2 (99%, Shanghai Hushi), 42g of CA50-A900 high-alumina cement (Henan Lite), and 5.2g of PVP (99%, Shanghai Aladdin).
[0049] The powder was placed in a planetary ball mill jar and mechanically mixed at high speed under no-load for 10 minutes to obtain a uniform white powder.
[0050] S2, Pulping and Molding
[0051] Add 130 mL of deionized water to the powder one at a time while stirring continuously for 30 minutes until a fluid mud-like consistency is formed.
[0052] The clay is loaded into a 5mm diameter molding die and pressed by a molding machine at 15MPa to obtain wet strips.
[0053] S3. Drying and calcination
[0054] Place the wet strips in an oven and dry them at 70°C for 8 hours.
[0055] Transfer to a muffle furnace, heat to 850℃, hold for 1 hour in air atmosphere, heating rate 10℃ / min.
[0056] After naturally cooling to room temperature, use pliers to cut the strip into 10mm segments, which are the prepared adsorbents.
[0057] S4, Cyclic Adsorption-Desorption Test
[0058] Instrument: Thermogravimetric analyzer (TGA), Program: Adsorption stage: temperature 650℃, atmosphere: 15% CO2 + 85% N2, total flow rate 100 ml / min, carbonation time 40 min; Desorption stage: temperature: 950℃, atmosphere: 100% CO2 atmosphere, total flow rate 100 ml / min, desorption time: 10 min; 50 cycles in total.
[0059] It should be noted that this embodiment also includes a comparative example using pure CaO adsorbent, i.e., without the addition of calcium-based adsorbent formed by high-alumina cement. The adsorption performance of this pure CaO adsorbent and the adsorbent obtained in Example 1 (represented as CaO + high-alumina cement) was further analyzed, and the results are as follows. Figures 3 to 5 As shown.
[0060] like Figure 3 As shown, the adsorption capacity in the first cycle reached as high as 0.48 g CO2 / g adsorbent, indicating excellent initial activity and high CaO conversion efficiency. In the first 10 cycles, the capacities of the high-alumina cement-doped adsorbent and the pure CaO adsorbent decreased rapidly, from 0.480 g / g to approximately 0.15 g / g and 0.46 g / g to 0.22 g / g, respectively, mainly due to the initial sintering of the CaO particle surface and adjustment of the pore structure. In the 10-20 cycles, the decay rate slowed down, and the capacity stabilized in the ranges of 0.18-0.22 g / g and 0.11-0.15 g / g, respectively, indicating that the Al2O3-CaO framework formed by the high-alumina cement began to play a structural stabilizing role. After 20 cycles, the high-alumina cement-doped sample retained approximately 45-50% of its initial capacity, significantly better than the unmodified calcium-based adsorbent. In other words, Figure 3 The curves shown exhibit a three-stage change: "rapid decay → slow decay → basically stable," demonstrating that the synergistic effect of high-alumina cement and PVP effectively inhibits the sintering of CaO and pore blockage, thus extending the service life of the material.
[0061] like Figure 4As shown in the adsorption curve of the tenth cycle, the adsorption capacity of the CaO + high-alumina cement system increased rapidly with time, reaching a stable value in about 10 minutes, with a final adsorption capacity of 200 mg / g. The adsorption rate of the CaO system was slightly slower than that of the CaO + high-alumina cement system, and the adsorption capacity after stabilization was 150 mg / g. This indicates that the adsorption capacity of the CaO + high-alumina cement system was significantly higher than that of pure CaO in the tenth cycle, reflecting the initial improvement of cycle stability by high-alumina cement.
[0062] like Figure 5 As shown, in the adsorption curves of the 20th cycle, the slope of the adsorption curve of the CaO + high-alumina cement system is close to that of the 10th cycle, and the adsorption capacity remains at 160 mg / g after stabilization, a decrease of 20% compared to the 10th cycle. The adsorption capacity of the CaO system further decreases to 110 mg / g, a decrease of 27% compared to the 10th cycle, with a faster decay rate. This indicates that CaO + high-alumina cement still maintains a higher adsorption capacity after 20 cycles, and the decay rate is smaller, confirming that the Al2O3-CaO framework formed by high-alumina cement effectively inhibits CaO sintering and extends the service life of the material.
[0063] This disclosure presents a calcium-based adsorbent, its preparation method, and its application, which have the following advantages compared to the prior art:
[0064] First, after calcination, CA50-A900 high-alumina cement forms a high-temperature resistant CaAl2O4 / CaAl4O7 crystalline phase, which acts as a physical barrier to prevent CaO particles from agglomerating and sintering, thus maintaining the integrity of the pore structure.
[0065] Secondly, although the multi-level channels formed by the thermal decomposition of PVP partially collapse during the cycle, the core interconnected channels can still be maintained, ensuring that the path for CO2 to diffuse into the interior of CaO is unobstructed; through the synergistic effect of high-alumina cement modification and PVP pore formation, the cycle stability and long-term activity of calcium-based adsorbent are significantly improved.
[0066] Third, the "dry mixing-wet conditioning" process ensures uniform dispersion of components, and the low-temperature calcination at 850℃ reduces excessive grain growth, further improving cycle stability.
[0067] It is understood that the above embodiments are merely exemplary embodiments used to illustrate the principles of this disclosure, and this disclosure is not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and substance of this disclosure, and these modifications and improvements are also considered to be within the scope of protection of this disclosure.
Claims
1. A method for preparing a calcium-based adsorbent, characterized in that, The preparation method includes: Using calcium hydroxide as the calcium source, high-alumina cement as the modifier, and polyvinylpyrrolidone as the pore-forming agent, the raw materials are mixed and deionized water is added to the mixed raw materials. The mixture is stirred to obtain a mud-like solid. The mud-like solid is pressed into long strips; The strip is dried, calcined, and trimmed to obtain a calcium-based adsorbent.
2. The preparation method according to claim 1, characterized in that, The mass ratio of the calcium source, the modifying agent, and the pore-forming agent is (220-225):(40-45):(5-6).
3. The preparation method according to claim 1, characterized in that, The mixing time for each ingredient is 8-12 minutes.
4. The preparation method according to claim 1, characterized in that, Add 100-150 mL of deionized water to the mixed raw materials and stir for 20-40 minutes.
5. The preparation method according to claim 1, characterized in that, The diameter of the strip is 4-6 mm.
6. The preparation method according to claim 1, characterized in that, The temperature for drying long strips is 65-75℃, and the time is 7-9 hours.
7. The preparation method according to claim 1, characterized in that, The temperature for calcining the strips is 800-900℃, and the time is 0.5-1.5h.
8. The preparation method according to claim 1, characterized in that, Trimming and finishing of long strips includes: Use pliers to cut the strip into 8-12mm segments.
9. A calcium-based adsorbent, characterized in that, The calcium-based adsorbent is prepared by the preparation method according to any one of claims 1-8.
10. An application of a calcium-based adsorbent, characterized in that, The calcium-based adsorbent described in claim 9 is used in CO2 adsorption / desorption.