Multistage core-shell structure composite particles for reversible reaction system and preparation method and application thereof

Abstract

The application discloses a kind of multistage core-shell structure composite particles for reversible reaction system and its preparation method and application, the multistage core-shell structure composite particles include active inner core layer, compressible flexible adhesive intermediate layer and metal oxide skeleton shell layer from inside to outside in sequence, wherein the compressible flexible adhesive intermediate layer includes vinylpyrrolidone-vinyl acetate copolymer.The multistage core-shell structure composite particles of the application have excellent high-temperature cycle stability, can effectively buffer the volume change in reversible reaction process, and have high mechanical strength and low wear rate.

Description

Technical Field

[0001] This invention relates to the field of reversible reactive functional materials engineering technology, and in particular to a multi-level core-shell structured composite particle for reversible reactive systems, its preparation method, and its application. Background Technology

[0002] In various reversible gas-solid or solid-solid reaction systems, active materials often face two fundamental failure mechanisms during repeated reactions: First, high-temperature sintering easily leads to irreversible degradation of reactivity. Under medium- and high-temperature conditions, the migration, growth, and pore structure collapse of the active phase grains significantly reduce the effective reaction interface. Second, reaction-induced volume changes easily lead to particle structural instability. Many reversible reactions are accompanied by significant molar volume changes, and repeated expansion and contraction generate periodic stress concentrations within the particles, ultimately leading to cracking, spalling, or pulverization. However, existing technologies mostly modify materials from the perspective of composition or simple blending, such as using doping with inert oxides, adding surface coatings, or creating overall pores to improve the performance of active materials. These methods typically have the following shortcomings: First, the different functional requirements of the active material in reversible reactions, such as reactivity, volume buffering, and sintering inhibition, are not structurally distinguished and they restrict each other, making it difficult to significantly improve overall performance. Second, the above methods may result in direct contact between the active phase and the high-modulus inorganic phase, causing stress concentration at the interface of the active material during cycling, which accelerates structural damage. Moreover, the modification effect of the above methods often depends on the specific material system and lacks a universal solution for the failure mechanism.

[0003] Therefore, there is an urgent need for a design scheme that does not rely on the modification of a single material, but starts from the particle structure level, and can synergistically regulate different failure mechanisms in repeated reversible reactions. This would provide a multi-level core-shell composite particle that can decouple reactivity, volumetric strain buffering and high-temperature structural stability. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention proposes a multi-level core-shell structured composite particle for reversible reaction systems, its preparation method, and its application. The aim is to provide a novel structural design scheme for active material particles that can simultaneously cope with the risk of high-temperature sintering and significant volume change stress in repeated reversible reaction processes (such as reversible gas-solid or reversible solid-solid reactions).

[0005] This invention provides a multi-level core-shell structured composite particle for reversible reaction systems, wherein the multi-level core-shell structured composite particle comprises, from the inside out, an active core layer, a compressible flexible adhesive intermediate layer, and a metal oxide skeleton outer shell layer;

[0006] The compressible flexible adhesive interlayer comprises a vinylpyrrolidone-vinyl acetate copolymer.

[0007] This invention constructs a multi-level core-shell structure within a single particle, enabling the creation of micron-scale composite particles that decouple reactivity, volumetric strain buffering, and high-temperature structural stability. By constructing distinct functional structural layers within a single particle—introducing a flexible buffering intermediate layer and a high-strength metal oxide outer shell—the essence lies in the sequential structural transformation of different functional materials at different temperature ranges, thereby forming an irreversible multi-level core-shell structure within the single particle. This structure exhibits excellent high-temperature cycling stability, effectively buffering volume changes during reversible reactions, and possesses high mechanical strength and low wear rate. It demonstrates significantly superior stability compared to existing technologies, particularly in high-temperature CO2 capture cycles and high-temperature thermochemical energy storage processes.

[0008] The compressible flexible adhesive interlayer of this invention coats the outside of the active core layer, forming a structural region with a certain porosity and deformable space in its final service state. This region preferentially absorbs and dissipates strain when the reactive inner layer undergoes volume expansion or contraction. The interlayer of this invention does not bear the main reactive activity during the reaction process; its function is to block the direct transmission of reaction-induced stress to the outer shell or inner layer interface, thereby avoiding interface failure caused by stress concentration. Using vinylpyrrolidone-vinyl acetate copolymer (VP / VA) as the main organic binder ensures that its decomposition sequence (thermal decomposition temperature range 300-500℃) during thermal evolution is prior to the activation of the core material (activation temperature range 600-900℃), and its decomposition temperature is lower than the stability temperature range of the metal oxide skeleton (900-1100℃). This ensures that the interlayer forms a continuous coating structure within the multi-level core-shell composite particles.

[0009] If PVA, PEG, or cellulose are used as organic binders, melting migration or carbon residue accumulation may occur within the decomposition temperature range of the intermediate layer material, making it difficult to form a stable buffer pore structure. For example, if vinylpyrrolidone (VP) is used as a single organic binder, its thermal decomposition temperature is relatively wide, and its initial decomposition temperature is high (usually above 400℃). The decomposition process may be accompanied by melting or softening, which can easily lead to uncontrollable gas escape paths and make it difficult to form ideal continuous and interconnected pores. The introduction of a single vinyl acetate (VA) unit, on the other hand, is difficult to maintain high-temperature stability due to the relatively weak thermal stability of its ester side chain. These units will preferentially undergo chain scission and depolymerization in the 300-500℃ range, and decompose first to produce gases (such as acetic acid, olefins, etc.), making it impossible to form a continuous coating structure. When VP / VA is used as an organic binder, VP can provide certain thermal stability and skeletal support during the decomposition of VA units, maintaining the initial shape of the polymer skeleton and preventing premature collapse. This "segmented decomposition" characteristic makes the decomposition initiation temperature of VP / VA copolymers lower, the decomposition rate more controllable, and the decomposition range more concentrated in the target temperature range (300-500℃).

[0010] Furthermore, the active core layer includes a core material and chopped fibers; the addition of chopped fibers can provide internal support for the core.

[0011] The core material includes any one or more of carbonates, metal hydroxides, metal oxides, alkali metal silicates, and alkali metal zirconates, such as CaCO3, Ca(OH)2, MgCO3, Mg(OH)2, Li4SiO4, Li2ZrO3, and SrCO3.

[0012] The failure mechanism is explained below using calcium-based core materials as an example: When the core material is mainly composed of CaCO3 and / or Ca(OH)2, it is converted into CaO after high-temperature calcination, which can serve as the main active phase for CO2 capture. The core has a connected porous structure, mainly providing CO2 adsorption capacity during repeated carbonation. However, similarly, the simple CaO / CaCO3 and CaO / Ca(OH)2 systems exhibit two failure mechanisms simultaneously during repeated reactions: irreversible decay of reactivity caused by high-temperature sintering and particle structure instability caused by reaction-induced volume changes. When this active material is applied to the functionally decoupled micron-sized composite particles of this invention, its adsorption capacity during reversible reactions can be largely retained, meaning it can function as carbon dioxide adsorption particles.

[0013] The following description uses calcium-based core materials as an example to illustrate the function of multi-level core-shell structured composite particles. First, the multi-level core-shell structured functional decoupling composite particles of this invention can significantly improve high-temperature cycling stability: under carbonation / calcination cycling conditions of 600-900℃, the calcium-based adsorbent particles can still maintain a stable CO2 adsorption capacity after multiple cycles, and the adsorption performance decay is significantly lower than that of existing single-structure calcium-based adsorbents. Because the metal oxide shell forms a continuous inorganic framework at high temperatures, it effectively restricts the migration and growth of CaO grains. The shell layer, as a physical isolation layer, also reduces the degree to which the calcium-based core is directly exposed to the high-temperature environment, thereby mitigating the specific surface area loss caused by high-temperature sintering. Secondly, the functionally decoupled composite particles with a specific multi-level core-shell structure of this invention can effectively buffer volume changes: the presence of a compressible flexible adhesive intermediate layer can significantly reduce the internal stress generated during carbonation / calcination, preventing particle structure instability. During repeated CO2 adsorption and regeneration, the particle structure remains intact, without obvious cracking, peeling, or pulverization. VP / VA decomposes at medium and low temperatures, forming a porous buffer layer with a certain compressibility. The fiber-reinforced material forms a spatial support network in the intermediate layer. When the calcium-based core expands or contracts in volume, the stress is first absorbed and dissipated in the intermediate layer, avoiding concentrated transmission to the shell or core interface. Furthermore, the functionally decoupled composite particles with a specific multi-level core-shell structure of this invention also possess high mechanical strength and low wear rate. The prepared calcium-based adsorption particles maintain high CO2 adsorption capacity while exhibiting high compressive strength and wear resistance, making them suitable for fluidized bed and fixed bed reactors. The calcium-based active core maintains high content and high porosity to ensure reaction activity, while the metal oxide shell provides overall mechanical support. Therefore, the multi-level core-shell structure achieves a functional division of "active inside and strong outside," avoiding the problem of the active phase being diluted by the inert phase in traditional blending systems.

[0014] Furthermore, the chopped fibers are any one or more of basalt fibers, alkali-resistant glass fibers, alumina fibers, quartz fibers, silicon carbide fibers, and stainless steel fibers.

[0015] Furthermore, the chopped fibers have a length of 100 μm-1 mm and a diameter of 5 μm-20 μm.

[0016] Furthermore, the particle size of the core material is 10-200 μm, preferably 25-75 μm.

[0017] Furthermore, the compressible flexible adhesive interlayer also includes a fiber-reinforced material.

[0018] Furthermore, the fiber reinforcement material is any one of basalt fiber or its biomimetic fiber, mineral fiber (such as alumina whiskers) or its biomimetic fiber.

[0019] Furthermore, the compressible flexible adhesive interlayer may also include a pore-forming agent.

[0020] Furthermore, the outer shell of the metal oxide framework is any one or more composite oxides selected from Mn-based oxides, Co-based oxides, and Cu-based oxides.

[0021] The metal oxide skeleton shell layer covers the outer side of the intermediate layer. Under conditions of 900-1100℃, the shell layer can form a continuous, dense, but porous inorganic skeleton structure. In the system of this invention, the design of the shell layer can provide the overall mechanical strength of the multi-level core-shell composite particles, while inhibiting high-temperature sintering of the core and improving the wear resistance of the particles in fluidized or fixed beds. After high-temperature heat treatment, the metal oxide shell can form an inorganic skeleton layer continuously distributed along the particle surface. This skeleton layer forms a closed stress transmission path on the outer periphery of the particle, redistributing the radial stress caused by core volume changes into tangential stress, thereby significantly reducing the risk of overall particle failure.

[0022] Furthermore, the multi-level core-shell composite particles are microspheres with a particle size of 100-500 μm.

[0023] This invention also provides a method for preparing the aforementioned multi-level core-shell composite particles, employing a process route combining microgranulation and fluidized bed coating, comprising the following steps: S1: Preparation of active core layer: Place the core material and chopped fibers (0.5-1.5 wt% of the core material) in a mixer, set the stirring speed to 200-400 rpm, and then add liquid binder: Spray a liquid binder with a concentration of 4-7 wt% (the liquid binder can be an ethanol solution or aqueous solution of vinylpyrrolidone-vinyl acetate copolymer, preferably an ethanol solution of vinylpyrrolidone-vinyl acetate copolymer) at a rate of 10-30 mL / min, start the bottom cutter, and increase the speed to 1000-1500 rpm. The wet material can be crushed and agglomerated (rounded) by high-frequency shearing force. The dense micron-sized core obtained after agglomeration is sieved to obtain a core with a particle size distribution of 80-250 μm. S2: Preparation of a compressible flexible adhesive intermediate layer: After obtaining the micron-sized core, a fluidized bed coating technology is used to achieve layered construction. The generated core is placed in a fluidized bed reactor (coating equipment), and hot air is turned on to make the particles in a "fluidized" state. The bed temperature is controlled at 50-72℃, and the intermediate layer is sprayed. The intermediate layer is sprayed with a slurry composed of vinylpyrrolidone-vinyl acetate copolymer (5-10wt% of slurry), fiber reinforcement material (1-3wt% of slurry), and solvent. The spraying rate is controlled at 2-8 g / min. A uniform flexible coating layer is formed on the surface of the core using a bottom spraying process to obtain the intermediate layer. S3: Preparation of metal oxide skeleton shell layer: Control the bed temperature at 50-72℃, and continue to introduce metal oxide slurry (solid content of 25-35wt%) into the fluidized bed reactor in multiple batches to obtain multi-layer structured particles. Multiple (two or more) small-batch spraying can ensure that the shell is dense and retains trace reaction channels. S4: Drying and heat treatment: The obtained multi-layer structure particles are dried at a temperature of 100-120℃ for 4-12 h. After drying, they are subjected to staged heat treatment: organic matter is decomposed at 300-500℃ for 1-4 h, so that the VP / VA in the middle layer decomposes to form a porous buffer structure. Then, the core material is activated at 600-900℃ for 1-3 h. The metal oxide skeleton is stabilized at 900-1100℃ for 0.5-2 h. At this temperature, the metal oxide shell forms a stable skeleton. After staged heat treatment and cooling, the multi-level core-shell structure composite particles are obtained.

[0024] This invention ensures that VP / VA undergoes thermal decomposition at medium and low temperatures through specific staged heat treatment, thereby forming flexible buffer pores within the particles. These pores buffer the volume changes of the core material during carbonation / calcination cycles, reducing internal stress concentration and preventing particle cracking. By using specific VP / VA as an organic binder in the intermediate layer and ensuring that its decomposition occurs before the activation of the core material, a continuous, flexible, porous buffer structure can be formed within the particles without disrupting the continuity of the outer shell. If the construction order of the intermediate and outer shell layers is changed, or if a one-time mixing granulation method is used to prepare multi-level core-shell composite particles, the thermal decomposition of VP / VA will directly affect the metal oxide layer, disrupting its continuity and preventing the formation of the aforementioned continuous stress-closed framework structure.

[0025] Furthermore, the average particle size of the core material in S1 is 10-200 μm.

[0026] Furthermore, the mass of the compressible flexible adhesive intermediate layer in S2 accounts for 8-15% of the mass of the multi-level core-shell structure composite particles. Thermogravimetric analysis (TGA) is used for testing. In an air atmosphere, the temperature is increased from room temperature to 600°C at a heating rate of 10°C / min. The mass percentage of the intermediate layer is determined by calculating the weight loss ratio between 300°C and 500°C.

[0027] Furthermore, the mass of the metal oxide skeleton shell layer in S3 accounts for 15-25% of the mass of the multi-level core-shell structure composite particles.

[0028] The present invention also provides the application of the multi-level core-shell structured composite particles in circulating fluidized bed reaction systems, high-temperature chemical energy storage devices, and as adsorbent materials for CO2 capture after high-temperature combustion, especially in high-temperature industrial flue gas CO2 removal and fixed-bed or moving-bed CO2 adsorption devices.

[0029] In summary, compared with the prior art, the present invention achieves the following technical effects: (1) The multi-level core-shell structured composite particles provided by the present invention can significantly improve high-temperature cycling stability; (2) The multi-level core-shell structured composite particles provided by the present invention can effectively buffer the volume change during the high-temperature reversible reaction process; (3) The multi-level core-shell structured composite particles provided by the present invention have high mechanical strength and low wear rate; (4) The multi-level core-shell structure composite particle preparation method provided by the present invention has clear process steps and strong controllability, and is suitable for industrial scale-up. Granulation, spheroidization, drying and heat treatment are all mature industrial unit operations that do not rely on complex chemical reactions or high-precision equipment. Each layer of structure is naturally formed through physical coating and heat treatment. The process window is wide and the repeatability is good. Attached Figure Description

[0030] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0031] Figure 1 The left figure is a three-dimensional structural schematic diagram of the multi-level core-shell structure composite particle of Embodiment 1 of the present invention, and the right figure is a cross-sectional structural schematic diagram of the multi-level core-shell structure composite particle of Embodiment 1 of the present invention. Figure 2 This is a schematic diagram of the preparation process of the multi-level core-shell structured composite particles in Embodiment 1 of the present invention; Figure 3 The left figure is a schematic diagram of the structural stability of traditional single-structure particles in a high-temperature reversible reaction system, and the right figure is a schematic diagram of the structural stability of multi-level core-shell structure composite particles in a high-temperature reversible reaction system according to Example 1 of the present invention. Explanation of reference numerals in the attached figures: 1: Active core layer; 2: Compressible flexible adhesive intermediate layer; 3: Metal oxide skeleton outer shell layer. Detailed Implementation

[0032] To enable those skilled in the art to better understand the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0033] Example The present invention will be further illustrated below with reference to specific embodiments and comparative embodiments. The following specific embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the following embodiments, and are not in particular limited to the types of raw materials used in the following specific embodiments.

[0034] I. The sources of raw materials for the examples and comparative examples are as follows: Unless otherwise specified, all raw materials used in the embodiments and comparative examples of this invention are commercially available.

[0035] II. Performance Testing Methods (1) Adsorption capacity test: Thermogravimetric analysis was performed using TGA. The test conditions were 650℃, 15% CO2, and 50mL / min.

[0036] (2) 50-cycle capacity retention test: Thermogravimetric analysis was used for the test. The adsorption test conditions were 650℃ and 15% CO2, and the regeneration conditions were 900℃ and 100% CO2.

[0037] (3) Particle cracking rate test: Randomly select 300-500 particles after cyclic testing and observe their surface morphology under a super depth-of-field microscope (VHX-6000). The judgment criteria are: the appearance of continuous cracks on the particle surface with a length exceeding 1 / 4 of the particle diameter, or the local peeling off of the outer shell layer, are recorded as cracking. The particle cracking rate is calculated by statistically analyzing the proportion of cracked particles.

[0038] (4) Particle wear rate test: The test shall be conducted in accordance with GB / T 30202.3-2013.

[0039] (5) Average compressive strength test: The test shall be conducted in accordance with GB / T 30202.3-2013.

[0040] (6) Sensible heat storage density test: The specific heat capacity from 25℃ to 900℃ was measured using a differential scanning calorimeter (DSC 214) under nitrogen atmosphere at a heating rate of 20 K / min. The heat storage value per unit mass was obtained by integral calculation.

[0041] (7) Thermal conductivity test: The transient planar heat source method is adopted. The particles to be tested are filled into a 50 mL standard container and compacted. A thin-layer probe is placed in the center of the container and the equivalent thermal conductivity of the packing state is measured at 25℃, GB / T 32064-2015.

[0042] (8) Test of skeleton integrity after cycling: After cycling, fine powder was removed by a 100-mesh standard sieve and the morphology of the remaining particles was statistically analyzed. Extremely high indicates that the shell is continuous, the structure is perfect, basically undamaged, and there are no obvious cracks; high indicates that local cracks have appeared; medium indicates that local cracks have occurred and the shell has peeled off over a large area; low indicates that the shell is severely broken.

[0043] Example 1 Example 1 describes the preparation of Mn-based multilevel core-shell composite particles with CaCO3 as the core material, comprising the following steps: S1: Preparation of active core layer: Calcium carbonate powder with an average particle size of 50 μm was used as the core material. Short-cut basalt fibers with a mass equivalent of 1.0 wt% of CaCO3 powder were added. The mixture was placed in a high-speed mixer and dry-mixed at a speed of 300 rpm. Then, an ethanol solution of vinylpyrrolidone-vinyl acetate copolymer with a mass concentration of 5 wt% was sprayed into the mixture at a rate of 20 mL / min as a binder. The bottom cutter was started and the speed of the mixer was increased to 1200 rpm. Spherical granules were formed by wet granulation. After sieving, regular spherical core particles with an average particle size of about 250 μm were obtained. S2: Preparation of compressible flexible adhesive intermediate layer: The obtained core particles are placed in a fluidized bed coating device, the fluidized bed temperature is set to 60℃, and a flexible layer slurry is prepared: the slurry contains 8wt% VP / VA copolymer and 2wt% alumina whiskers, and the solvent is ethanol. The slurry is uniformly applied to the surface of the fluidized core particles at a spraying rate of 5 g / min. By controlling the spraying rate and drying process, the intermediate layer is formed with a mass of 10wt% of the particle mass, thus obtaining particles coated with a compressible flexible adhesive intermediate layer. S3: Metal oxide outer shell coating: Prepare a manganese dioxide (MnO2) slurry with a solid content of 30wt%, and place the particles coated with the above-obtained compressible flexible adhesive intermediate layer in a fluidized bed. Spray the above-obtained MnO2 slurry three times, allowing sufficient drying time after each spraying to avoid particle agglomeration. Keep the outer shell material mass at 20wt% of the total particle mass to obtain multi-stage coated particles. S4: Drying and heat treatment: The above-mentioned multi-level coated particles were placed in a drying oven and dried at 100℃ for 8 h to remove free water. Then, the dried particles were placed in a tube furnace for staged heat treatment under the following conditions: the temperature was raised to 400℃ and held for 2 h to decompose VP / VA and form a porous buffer structure inside the particles. The temperature was then raised to 800℃ and held for 2 h to convert calcium carbonate into calcium oxide. The temperature was raised to 1000℃ and held for 1 h to form a stable and continuous inorganic framework structure of the metal oxide shell. After cooling, multi-level core-shell structure calcium-based carbon dioxide adsorbent particles with a particle size of 280-380 μm were obtained.

[0044] Example 2 Example 2 describes the preparation of Mn-based multilevel core-shell composite particles with CaCO3 as the core material, comprising the following steps: S1: Preparation of active core layer: Calcium carbonate powder with an average particle size of 150 μm was used as the core material, and short-cut basalt fibers equivalent to 1.5 wt% of CaCO3 powder were added. The mixture was placed in a high-speed mixer and dry-mixed at a speed of 400 rpm. Then, an ethanol solution of vinylpyrrolidone-vinyl acetate copolymer with a mass concentration of 4 wt% was sprayed into the mixture at a rate of 30 mL / min as a binder. The bottom cutter was started, and the speed of the mixer was increased to 1500 rpm. Spherical granules were formed by wet granulation. After sieving, regular spherical core particles with an average particle size of about 250 μm were obtained. S2: Preparation of compressible flexible adhesive intermediate layer: The obtained core particles are placed in a fluidized bed coating device, the fluidized bed temperature is set to 70℃, and a flexible layer slurry is prepared: the slurry contains 10wt% VP / VA copolymer and 2wt% alumina whiskers, and the solvent is ethanol. The slurry is uniformly applied to the surface of the fluidized core particles at a spraying rate of 8 g / min. By controlling the spraying rate and drying process, the intermediate layer is formed with a mass of 12wt% of the particle mass, thus obtaining particles coated with a compressible flexible adhesive intermediate layer. S3: Metal oxide outer shell coating: Prepare a manganese dioxide (MnO2) slurry with a solid content of 35 wt%. Place the particles coated with the above-mentioned compressible flexible adhesive intermediate layer in a fluidized bed and spray the above-mentioned MnO2 slurry three times. Sufficient drying time is allowed after each spraying to avoid particle agglomeration. The outer shell material accounts for 23 wt% of the total particle mass, thus obtaining multi-stage coated particles. S4: Drying and heat treatment: The above-mentioned multi-stage coated particles were placed in a drying oven and dried at 120℃ for 6 h to remove free water. Then, the dried particles were placed in a tube furnace for staged heat treatment under the following conditions: the temperature was raised to 350℃ and held for 3 h to decompose VP / VA and form a porous buffer structure inside the particles. The temperature was then raised to 650℃ and held for 3 h to convert calcium carbonate into calcium oxide. The temperature was raised to 1000℃ and held for 1 h to form a stable and continuous inorganic framework structure of the metal oxide shell. After cooling, multi-stage core-shell structure calcium-based carbon dioxide adsorbent particles with a particle size of 380-480 μm were obtained.

[0045] Example 3 Example 3 describes the preparation of calcium-based carbon dioxide adsorbent particles with different metal oxide shells. Except for replacing the manganese-based oxide manganese dioxide slurry in Example 1 with a composite slurry of cobalt oxide (Co3O4) and copper oxide (CuO) mixed in a mass ratio of 1:1, the other preparation steps and process conditions are the same as in Example 1.

[0046] Example 4 Example 4 prepared calcium-based carbon dioxide adsorbent particles with different intermediate layer masses. Based on Example 1, the amount of intermediate layer coating slurry added during the coating process was adjusted to increase the proportion of flexible adhesive intermediate layer in the final particle mass fraction to 15 wt%. The remaining preparation steps and process conditions were the same as in Example 1.

[0047] Example 5 Example 5 prepared calcium-based carbon dioxide adsorbent particles with different intermediate layer masses. Based on Example 1, the amount of intermediate layer coating slurry added during the coating process was adjusted so that the flexible adhesive intermediate layer accounted for 6 wt% of the final particle mass. The remaining preparation steps and process conditions were the same as in Example 1.

[0048] Example 6 The difference between Example 6 and Example 1 is that the core material is Li4SiO4, while the rest of the preparation steps and process conditions are the same as in Example 1.

[0049] Comparative Example 1 Comparative Example 1: Traditional blended particles without multi-level structure were prepared by physically mixing and granulating CaCO3 powder, chopped basalt fiber, binder, flexible layer slurry and MnO2 powder used in Example 1 in the same total composition ratio as the final product of Example 1. The resulting particles were then dried and calcined at 800°C for 2 h to convert calcium carbonate into calcium oxide, thus obtaining monolayer calcium-based adsorption particles.

[0050] Comparative Example 2 Comparative Example 2 prepared calcium-based adsorbent particles without a compressible flexible adhesive interlayer. Except for skipping the step of preparing the compressible flexible adhesive interlayer, the other steps were the same as in Example 1. That is, after obtaining the CaCO3 core particles, the same mass of MnO2 slurry was directly sprayed onto their surface, followed by the same drying treatment, heat treatment at 800°C for 2 h, and then heat treatment at 1000°C for 6 h. The resulting particles had a direct "core-shell" structure and lacked an intermediate flexible / buffer layer.

[0051] Comparative Example 3 Comparative Example 3 prepared calcium-based adsorbent particles with other flexible interlayer binder components. Except for step S2, in which the binder in the slurry was replaced by an equal mass of polyvinyl alcohol (PVA) instead of VP / VA copolymer, the other preparation steps and process conditions were the same as in Example 1.

[0052] The particles obtained in Examples 1-6 and Comparative Examples 1-3 were placed in a fluidized bed reactor for high-temperature CO2 capture cycle testing (adsorption: 650℃, 15% CO2; regeneration: 900℃, 100% CO2). The carbon dioxide adsorption performance results are as follows: Table 1. Adsorption performance of the examples and comparative examples

[0053] Table 2. Mechanical properties and thermal storage performance of the examples and comparative examples.

[0054] Examples 1-6 simultaneously introduced an active core layer, a compressible flexible adhesive intermediate layer, and a metal oxide framework outer shell to prepare multi-level core-shell composite particles. A specific vinylpyrrolidone-vinyl acetate copolymer was used as the intermediate layer binder. The resulting multi-level core-shell composite particles exhibited both high adsorption performance and high structural stability during high-temperature cyclic thermal storage and CO2 capture, making them suitable for industrial application. Examples 1-3 formed a multi-level core-shell structure comprising a calcium-based active core, a compressible flexible adhesive intermediate layer, and a metal oxide framework outer shell, demonstrating good structural stability and mechanical strength during high-temperature CO2 capture cycles. In Example 4, the compressible flexible adhesive intermediate layer accounted for 15 wt%, and the resulting particles exhibited stronger volume change buffering capacity during repeated carbonation / calcination, further improving particle integrity. Example 6 used other core materials, yet still achieved both high adsorption performance and high structural stability during high-temperature cyclic thermal storage and CO2 capture.

[0055] Comparative Examples 1-3 are all compared with Example 1. Comparative Example 1 prepared traditional blended particles without a multi-level structure. During the high-temperature CO2 capture cycle, the calcium-based particles were directly exposed to the high-temperature environment, and the CaO grains were prone to rapid sintering. The volume changes caused by carbonation / calcination could not be buffered, resulting in internal stress concentration, which made the particles prone to cracking and pulverization, and had poor mechanical strength and cycle stability. The calcium-based adsorbent particles prepared in Comparative Example 2 lacked a compressible flexible adhesive interlayer. Since the coefficients of thermal expansion of calcium-based materials (such as CaCO3) and active shell materials (such as MnO2) are significantly different, without a flexible buffer layer with elasticity and porosity, huge shear stress will be generated at the interface of the two rigid materials due to thermal mismatch during heat treatment and use. This directly leads to cracks in the outer shell and even peeling off from the core. This structural failure causes the active outer shell to lose its integrity, the core to be exposed and pulverized, and the particle lifespan to be drastically shortened. In contrast, this invention forms a clear core-shell structure through hierarchical granulation, achieving functional separation of activity and strength. In Comparative Example 3, the compressible flexible adhesive interlayer uses PVA as the binder. Its decomposition and pore-forming kinetics during heat treatment differ from those of VP / VA in this invention, easily leading to a poor pore structure in the final buffer layer (such as too low porosity or uneven distribution). Its elastic modulus and bonding strength fail to reach the optimal state. At the same time, since the interfacial bonding between PVA and inorganic fibers / whiskers is weaker than that of VP / VA, the overall mechanical strength (such as compressive strength) and thermal shock resistance of the particles are easily reduced. None of the above comparative examples can obtain multi-level core-shell structure composite particles that simultaneously possess decoupled reactivity, volumetric strain buffering, and high-temperature structural stability.

[0056] Based on the test data in Table 1 regarding the adsorption capacity, capacity retention rate after 50 cycles, particle cracking rate, and wear rate obtained after high-temperature CO2 capture cycling tests on the prepared multi-level core-shell composite particles, and the test data in Table 2 regarding the average compressive strength, sensible heat storage density, thermal conductivity, and skeleton integrity after cycling of the multi-level core-shell composite particles, it can be seen that by constructing a multi-level core-shell structure with clearly defined functions from the inside out within the particles: the active core provides the main CO2 adsorption activity, the compressible flexible adhesive intermediate layer formed by the thermal decomposition of VP / VA effectively buffers the volume change of calcium-based materials during carbonation / calcination, and the metal oxide shell forms a stable skeleton under high-temperature conditions, inhibiting sintering and improving the overall mechanical strength of the particles, it is possible to obtain active material particles that remain stable while simultaneously coping with the risk of high-temperature sintering and significant volume change stress during repeated reversible reactions. Therefore, Examples 1-6 of this invention have significant advantages over the comparative examples and can effectively meet the high standards required by customers and the market.

[0057] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing multi-level core-shell structured composite particles, characterized in that, Includes the following steps: S1: Preparation of active core layer: Place the core material and chopped fibers in a mixer, set the stirring speed to 200-400 rpm, and then add liquid binder: spray in a liquid binder with a concentration of 4-7 wt% at a rate of 10-30 mL / min, start the bottom cutter, increase the speed to 1000-1500 rpm, agglomerate and sieve to obtain micron-sized core; S2: Preparation of compressible flexible adhesive intermediate layer: After obtaining the micron-sized core, the fluidized bed coating technology is used to achieve layered construction. The generated core is placed in a fluidized bed reactor, hot air is turned on, and the bed temperature is controlled at 50-72℃. The intermediate layer is sprayed with a slurry composed of vinylpyrrolidone-vinyl acetate copolymer, fiber reinforcement material and solvent, and the spraying rate is controlled at 2-8 g / min to obtain the intermediate layer. S3: Preparation of metal oxide framework outer shell: Control the bed temperature at 50-72℃, and continue to introduce metal oxide slurry into the fluidized bed reactor in multiple batches to obtain multi-layer structured particles; S4: Drying and heat treatment: The obtained multi-layer structure particles are dried and then subjected to staged heat treatment: organic matter is decomposed at 300-500℃ for 1-4 h, the core material is activated at 600-900℃ for 1-3 h, the metal oxide skeleton is stabilized at 900-1100℃ for 0.5-2 h, and after cooling, the multi-level core-shell structure composite particles are obtained. The multi-level core-shell structured composite particles are used in reversible reaction systems, and from the inside out, they include an active core layer, a compressible flexible adhesive intermediate layer, and a metal oxide skeleton outer shell layer. The compressible flexible adhesive interlayer comprises a vinylpyrrolidone-vinyl acetate copolymer; The active core layer comprises a core material and short-cut fibers; The core material includes any one or more of carbonates, metal hydroxides, metal oxides, alkali metal silicates, and alkali metal zirconates; The compressible flexible adhesive interlayer also includes fiber reinforcement material; The outer shell of the metal oxide framework is any one or more composite oxides selected from Mn-based oxides, Co-based oxides, and Cu-based oxides; The multi-level core-shell composite particles are microspheres with a particle size of 100-500 μm.

2. The preparation method according to claim 1, characterized in that, The average particle size of the core material in S1 is 10-200 μm.

3. The preparation method according to claim 1, characterized in that, In the S2, the mass of the compressible flexible adhesive intermediate layer accounts for 8-15% of the mass of the multi-level core-shell structure composite particles.

4. The preparation method according to claim 1, characterized in that, In the S3, the mass of the metal oxide skeleton shell layer accounts for 15-25% of the mass of the multi-level core-shell structure composite particles.

5. The application of the multi-level core-shell structured composite particles prepared by the preparation method according to any one of claims 1-4 as an adsorbent material for CO2 capture after high-temperature combustion.

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