A calcium-nickel-based composite material for a photo-thermal fluidized bed and a preparation method and application thereof

Abstract

This invention discloses a calcium-nickel-based composite material for photothermal fluidized beds, its preparation method, and its application. The calcium-nickel-based composite material uses components including a calcium source, a framework source, a photothermal catalyst source, and a pore-forming agent as raw materials. Its structure has a connected microporous network formed by the pyrolysis of the pore-forming agent and a composite inorganic metal oxide framework doped with metal elements. It is prepared by extrusion-spheronization and calcination-reduction-acidification processes. This invention constructs a highly connected pore network and a calcium-aluminum composite oxide framework inside the material through the synergistic doping of Al-Ni or Al-Co-Ni multi-metals. This material successfully overcomes the defects of traditional calcium-based particles, such as easy sintering and easy pulverization, and has excellent mechanical compressive strength, high full-spectrum absorption rate, excellent cycle stability, and efficient intrinsic catalysis and anti-carbon deposition ability, making it suitable for the large-scale, long-cycle operation requirements of photothermal fluidized bed conditions.

Description

Technical Field

[0001] This invention relates to a calcium-nickel-based composite material, particularly to a calcium-nickel-based composite material for photothermal fluidized beds, and also to a method for preparing and applying the aforementioned calcium-nickel-based composite material. Background Technology

[0002] Solar thermal methane-calcium cycle dry reforming technology couples carbon capture with resource utilization. This technology uses solar energy as the driving heat source. First, calcium-based materials capture carbon dioxide to form calcium carbonate. Then, under sunlight and high temperature, the calcium carbonate decomposes, releasing high-concentration carbon dioxide, which reacts with introduced methane in the presence of a metal catalyst to produce syngas. In this process system, the fluidized bed reactor, due to the intense gas-solid turbulence of the internal particles, exhibits high thermal response and heat transfer efficiency. Particulate materials typically have a large specific surface area, providing more active sites for the reaction and facilitating the loading of catalysts and microwave-absorbing materials, achieving multifunctional integration of the heat storage medium. The high mechanical strength of the particulate materials results in low wear during the intense fluidization process, maintaining the original mechanical structure and facilitating continuous and large-scale reaction operation.

[0003] Although particulate calcium-based materials exhibit good engineering applicability in the aforementioned systems, unmodified calcium-based materials face a technical bottleneck of poor cycle stability. On the one hand, during repeated calcination decomposition and carbonation cycles, the molar volume of calcium carbonate is 36.9 cm³. 3 / mol, while the molar volume of calcium oxide is 16.7 cm³. 3 Drastic volume changes, such as those occurring at a rate of / mol, can induce stress concentration, pore collapse, and surface sintering within the particles, leading to agglomeration and deactivation of calcium oxide particles. This results in a significant and irreversible decrease in the material's effective utilization rate, carbon dioxide adsorption capacity, and energy storage density. Furthermore, in photothermal driven systems, the spectral absorption characteristics of the medium directly determine the system's photothermal conversion efficiency. Traditional calcium carbonate and calcium oxide particles primarily exhibit a light grayish-white surface with extremely low intrinsic spectral absorbance (approximately 19.50%), meaning most of the irradiated light energy is reflected or scattered, severely limiting the system's photothermal conversion efficiency. In addition, methane dry reforming reaction systems have high reaction barriers, typically requiring the introduction of catalysts into calcium-based materials to promote the reaction and improve conversion rates. Simultaneously, the dense structure and sparse pores of pure calcium-based materials severely hinder mass transfer and diffusion of reactant gases within the material.

[0004] To overcome mass transfer resistance and gas diffusion bottlenecks, existing technologies typically introduce organic pore-forming agents for porosimetry modification. However, the introduction of porous structures disrupts the structural continuity of the material, leading to a reduction in the mechanical strength of the particles, with the maximum compressive load often falling below 1 N. Under the long-term continuous airflow disturbance, particle collisions, and friction environment of a fluidized bed, porous particles with reduced mechanical strength are highly susceptible to breakage and failure, failing to meet the wear resistance requirements for long-term stable operation. To further overcome these performance bottlenecks, existing technologies in this field attempt to introduce external metal elements for composite doping modification. Common practices include doping with transition metals that possess both catalytic and microwave absorption functions (such as Ni), or further composited with other metals (such as Mg, Zn, etc.) as structural stabilizers. However, existing composite materials still suffer from limitations in achieving multiple performance goals under actual photothermal fluidized bed conditions. For example, while nickel doping can improve light absorption, the lack of a stable inorganic framework results in low mechanical strength and resistance to sintering. Magnesium doping readily reacts with the calcium-based support during high-temperature preparation or reaction, forming a calcium-magnesium carbonate solid solution impurity. This impurity not only has low mechanical strength but also dissipates some catalytic or absorbing active sites, leading to a significant decrease in the material's intrinsic spectral absorption capacity. Zinc doping, while improving the porous structure to some extent, significantly reduces the proportion of effective energy storage components, causing a sharp decline in energy density during high-temperature cycling and a lack of long-term thermal stability. Therefore, existing multi-component doping schemes struggle to achieve synergistic improvements in multiple performance objectives.

[0005] Given the aforementioned technological limitations, there is an urgent need in this field to design a calcium-nickel-based composite material that possesses high mechanical strength, high resistance to sintering cycle stability, strong spectral absorption capacity, and high catalytic activity, and can be perfectly adapted to photothermal fluidized bed conditions. Summary of the Invention

[0006] Purpose of the invention: The purpose of this invention is to provide a calcium-nickel-based composite material for photothermal fluidized beds that has excellent mechanical and wear-resistant properties, high full-spectrum absorption performance, long cycle life, high intrinsic catalytic activity, and excellent anti-coking ability. The invention also provides a method for preparing the above-mentioned calcium-nickel-based composite material and its application in photothermal methane dry reforming fluidized bed systems or calcium circulating carbon capture systems.

[0007] Technical Solution: The present invention relates to a calcium-nickel-based composite material for photothermal fluidized beds, using components including a calcium source, a framework source, a photothermal catalyst source, and a pore-forming agent as raw materials. Its structure comprises a connected microporous network formed by the pyrolysis of the pore-forming agent and a composite inorganic metal oxide framework doped with metal elements. The surface of the composite material is distributed with catalytically active metallic Ni. 0 And oxygen vacancies.

[0008] The calcium source includes a calcium-containing compound, the photothermal catalytic source includes a nickel-containing compound, the framework source includes an aluminum-containing compound or a combination of an aluminum-containing compound and a cobalt-containing compound, the inorganic metal oxide framework is a calcium-aluminum composite oxide framework, and the molar ratio of each metal element in the composite material is Ca:Al:Co:Ni = 100:5~15:0~5:8~15. Preferably, the molar ratio is any one of the following: Ca:Al:Co:Ni = 100:10:2:12, Ca:Al:Ni = 100:12:12 or Ca:Al:Ni = 100:10:12.

[0009] The calcium-containing compound includes at least one of calcium hydroxide, calcium oxide, inorganic calcium salt, or organic calcium salt; the pore-forming agent is selected from at least one of cellulose, polysaccharide, polymer, or carbon-based material; the nickel-containing compound is selected from at least one of soluble inorganic nickel salt or organic nickel salt; the aluminum-containing compound is selected from at least one of soluble inorganic aluminum salt or organic aluminum salt; and the cobalt-containing compound is selected from at least one of soluble inorganic cobalt salt or organic cobalt salt. Preferably, the calcium-containing compound is calcium hydroxide, the pore-forming agent is microcrystalline cellulose, the nickel-containing compound is nickel nitrate, the aluminum-containing compound is aluminum nitrate, and the cobalt-containing compound is cobalt nitrate.

[0010] The above-mentioned method for preparing calcium-nickel-based composite materials for photothermal fluidized beds employs an extrusion-spheronization process and a calcination-reduction-acidification process, and includes the following steps:

[0011] (1) The photothermal catalyst source and the framework source are fully dissolved in a solvent to obtain a mixed solution. The calcium source and the pore-forming agent are mixed and added to the mixed solution and stirred thoroughly to obtain a slurry.

[0012] (2) The slurry is extruded to obtain a strip sample, and then the strip sample is rolled into a ball to obtain a granular mixture;

[0013] (3) The granular mixture is calcined to pyrolyze the pore-forming agent and obtain calcined granules with a porous structure;

[0014] (4) The calcined particles are subjected to reduction treatment and acidification treatment in sequence to obtain the calcium-nickel based composite material facing the photothermal fluidized bed.

[0015] In step (1), the solvent is water, and the mixing ratio of the calcium source and the pore-forming agent is: per 1 mol Ca 2+ Add 10-20g of pore-forming agent accordingly, preferably per 1mol Ca 2+ Add 15g of pore-forming agent accordingly.

[0016] In step (3), the heating procedure for the calcination treatment is as follows: the temperature is raised from room temperature to 450-550℃ at a rate of 1-3℃ / min and held for 1-3 hours, then raised to 750-850℃ at the same rate and calcined for 1-2 hours. Preferably, the temperature is raised from room temperature to 500℃ at a rate of 2℃ / min and held for 2 hours, then raised to 800℃ at a rate of 2℃ / min and calcined for 1 hour.

[0017] In step (4), the reduction treatment conditions are as follows: under an atmosphere containing reducing gas, the temperature is increased to 650-750℃ for 1-3 hours at a heating rate of 5-15℃ / min, preferably to 700℃ for 2 hours at a heating rate of 10℃ / min; the acidification treatment conditions are as follows: acidification treatment is performed for 1-3 hours under an atmosphere containing acidic gas, preferably for 2 hours; the atmosphere containing reducing gas is a reducing atmosphere containing H2, and the atmosphere containing acidic gas is a pure CO2 atmosphere.

[0018] The aforementioned calcium-nickel-based composite materials for photothermal fluidized beds can be applied in photothermal methane calcium cycle dry reforming systems or calcium cycle carbon capture systems. Furthermore, they can be applied in fluidized bed reactors and large-scale energy conversion and storage systems.

[0019] Invention principle: This invention achieves multi-dimensional synergistic enhancement of materials in terms of structural mechanics, spectral absorption and catalytic activity through the scientific compounding of multiple metal components such as Al, Co and Ni and the extrusion-spheronization process.

[0020] In terms of structural mechanics and thermal stability, this invention utilizes the interconnected microporous network formed by the pyrolysis of a pore-forming agent (microcrystalline cellulose) to provide mass transfer channels. Furthermore, by doping aluminum elements and reacting them with the calcium matrix at high temperatures, a high-hardness calcium-aluminum composite oxide framework, represented by Ca5(Al3O7)2, is generated. This framework effectively fills the structural defects caused by pore formation, playing a crucial mechanical support role. This significantly increases the average maximum compressive load of the particles from 0.82N in pure calcium-based materials to over 6.30N (as high as 6.79N in Example 1), ensuring the material can withstand the intense gas-solid collisions under fluidized bed conditions. Simultaneously, this framework acts as a physical barrier, increasing the Taman temperature of the material and effectively inhibiting the agglomeration and sintering of active CaO grains during high-temperature cycling, significantly improving cycling stability. Experiments show that the energy density decay rate of Al-Co-Ni co-doped materials after 20 cycles is only 17.05% (from 1940.86 kJ / kg to 1648.59 kJ / kg), which is far better than the decay rate of 45.68% of pure calcium-based materials.

[0021] In terms of spectral absorption and chemical activity, the specially selected metal components achieved the coupling of photothermal and catalytic functions. On the one hand, the introduction of Ni provides intrinsic optical absorption sites, while the interconnected porous network stably supported by Al increases the multiple diffuse reflections of incident light within the material. This synergistic effect of structure and composition significantly reduces the band gap of the material, causing the average spectral absorbance to jump from 19.50% in pure CaCO3 to over 87.17% (Ca100Al10Co2Ni12), an increase of approximately 4.51 times. On the other hand, the synergistic effect of Al and Co alters the chemical environment of Ni through electronic regulation, significantly promoting the reduction of Ni oxides. XPS characterization shows that the introduction of Al and Co enables catalytically active metallic Ni... 0 The proportion increased from 22.92% when Ni was doped alone to over 31.58%; at the same time, it induced abundant oxygen vacancies, enhancing the lattice oxygen migration ability. This surface chemical state not only effectively reduced the barrier to the dry reforming reaction of methane, but also promoted the oxidation and elimination of surface carbon, endowing the material with excellent intrinsic catalytic activity and anti-coking ability.

[0022] Regarding the optimization of component ratios, the metal molar ratio specified in this application (e.g., preferably Ca:Al:Co:Ni = 100:10:2:12) is crucial for balancing mechanical strength, energy storage density, and catalytic activity. The amount of Al doping ensures sufficient construction of a stable framework to maintain structural integrity, without significantly reducing the proportion of the CaO bulk energy storage due to excessive doping. The introduction of trace amounts of Co maximizes the activation of Ni's reduction potential without compromising Al's control over the porous structure, avoiding the formation of Mg as seen in Mg doping (Comparative Example 3). 0.03 Ca 0.97 The material exhibits a simultaneous degradation in mechanical strength (0.80 N) and absorptivity (59.30%) due to low-strength impurities such as CO3. By precisely proportioning each component, the optimal balance between mechanical support, efficient photothermal conversion, and long-lasting catalytic performance was achieved.

[0023] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages:

[0024] (1) In terms of structure and mechanical properties, it combines a highly interconnected porous structure with excellent wear resistance. This invention successfully overcomes the technical defects of conventional porous particles, such as easy pulverization and low strength, by supporting the calcium-aluminum composite oxide skeleton. The average maximum compressive load of the composite particles of this invention reaches more than 6.30N, and can reach 6.79N under the optimal ratio, which is much higher than 0.82N of unmodified pure calcium-based materials and 0.70N of materials with only physical pore formation, and can completely withstand the severe gas-solid collision and wear under fluidized bed conditions;

[0025] (2) In terms of optical performance, the capture of solar energy and the efficiency of photothermal conversion have undergone a qualitative change. Due to the synergistic effect of the intrinsic absorption of Ni and the diffuse reflection of the interconnected porous network, the material of this invention has an average spectral absorption rate of more than 87.17% in the 300-2500nm band (up to 87.88%), which is about 4.51 times higher than the absorption rate of only 19.50% of the unmodified pure calcium-based material, greatly enhancing the photothermal conversion efficiency of the system in the full spectrum range;

[0026] (3) In terms of thermodynamic properties, it achieves excellent anti-sintering effect and ultra-long cycle life. After 20 cycles of calcination-carbonation alternation at 800℃, the energy storage density decay rate of the material of this invention is as low as 17.05% due to the physical barrier effect of the inorganic skeleton. In contrast, the decay rate of pure calcium-based materials is as high as 45.68%, and the decay rate of physical pore-forming materials is as high as 51.11%. The energy storage density of the material of this invention is always maintained above 1648.59kJ / kg, and the CaO conversion rate is maintained above 60%, showing excellent anti-sintering performance and long-cycle thermal stability.

[0027] (4) In terms of chemical activity, it significantly lowers the reaction barrier of methane dry reforming and enhances the resistance to carbon deposition. The electronic regulation effect of multiple metals promotes the high activity of metallic Ni on the material surface. 0 The proportion of [agent] increased to over 31.58%, a significant improvement compared to the 22.92% of the single-doped Ni material without synergistic regulation. Simultaneously, the synergistic effect induced abundant surface oxygen vacancies, greatly enhancing the intrinsic catalytic efficiency of the material and effectively promoting the oxidation and elimination of surface carbon.

[0028] (5) In terms of preparation process, the method is precise and controllable, with high molding quality, and has excellent prospects for industrial application. The present invention adopts the "extrusion-spheroidization" molding process, which can precisely control the size of the composite particles (e.g., 0.4 mm diameter) and the regular spherical morphology, ensuring the uniform fluidization quality of the material in the reactor. At the same time, the step-by-step temperature-programmed calcination process (e.g., holding at 500℃ first and then calcining at 800℃) allows the microcrystalline cellulose to be pyrolyzed slowly and thoroughly, ensuring the uniform formation of internal interconnected pores and avoiding structural collapse caused by violent gas release. The overall process conditions are mild and reproducible, making it extremely suitable for large-scale, continuous industrial production. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the preparation process of the calcium-nickel based composite material for photothermal fluidized beds according to the present invention;

[0030] Figure 2 The image shown is a scanning electron microscope (SEM) image of the calcium-nickel based composite material prepared in Example 1 of the present invention, used to illustrate its internal interconnected microporous network structure.

[0031] Figure 3 The X-ray diffraction (XRD) pattern of the calcium-nickel based composite material prepared in Example 1 of the present invention is used to illustrate the calcium-aluminum composite oxide skeleton generated inside it. Detailed Implementation

[0032] The present invention will now be described in detail with reference to specific embodiments, and the performance parameters involved were measured according to the following standards:

[0033] Specific surface area and pore volume: The results were obtained by low-temperature liquid nitrogen adsorption method (77.35 K) after degassing at 200℃ using an ASAP 2460 analyzer.

[0034] Spectral absorbance: Measured using a Lambda 1050+ spectrophotometer in the wavelength range of 300–2500 nm;

[0035] Mechanical strength: Using a ZP-50N digital display push-pull force gauge, a single particle was placed between two parallel pressure plates and pressure was applied until macroscopic crushing, and the peak value of the maximum compressive load was recorded;

[0036] Cyclic stability: The test was conducted using a TGA / DSC 3+ synchronous thermal analyzer, with 20 cycles of alternating pure N2 calcination and pure CO2 carbonation at 800℃.

[0037] Example 1

[0038] The calcium-nickel-based composite material for photothermal fluidized beds of the present invention is prepared by the following method: Figure 1 As shown, it includes the following steps:

[0039] (1) Based on the molar ratio of metal elements Ca:Al:Co:Ni = 100:10:2:12, weigh out the corresponding nickel nitrate, aluminum nitrate, and cobalt nitrate, and dissolve them thoroughly in deionized water to obtain a mixed solution. Weigh out calcium hydroxide powder and microcrystalline cellulose, and mix them according to the ratio of 1 mol Ca... 2+ Mix the ingredients evenly according to the ratio of 15g microcrystalline cellulose, then add them to the above mixed solution and stir thoroughly to make a slurry in which the components are evenly dispersed.

[0040] (2) The obtained slurry is fed into an extruder and extruded to obtain strip samples with a diameter of 0.4 mm. The strip samples are then fed into a spherical baller to form spherical particles and sieved.

[0041] (3) The sieved particles were transferred to a muffle furnace for calcination. The temperature was increased from room temperature to 500°C at a rate of 2°C / min and held for 2 hours. Then the temperature was increased to 800°C at a rate of 2°C / min and calcined for 1 hour to allow the organic matter to pyrolyze and form pores and a metal oxide framework.

[0042] (4) The calcined particles were placed in a tube furnace for reduction and acidification treatment. The temperature was increased to 700℃ for 2h at a heating rate of 10℃ / min under a mixed atmosphere of 10 vol% H2 / Ar. Then the atmosphere was switched to pure CO2 for acidification treatment for 2h to obtain the calcium-nickel based composite material, denoted as Ca100Al10Co2Ni12.

[0043] The composite particles form a porous network with excellent connectivity and a calcium-aluminum composite oxide framework. For example... Figure 2 and Figure 3 As shown, by Figure 2 Scanning electron microscopy images show that the composite material exhibits a highly developed and interconnected porous network structure with numerous honeycomb-like micropores distributed on its surface. This structure arises from the fact that the Al₂O₃ generated during calcination by the doped aluminum effectively inhibits the excessive sintering of CaCO₃, preserving abundant intergranular pores. Furthermore, the introduction of 2 mol% cobalt did not disrupt the regulatory effect of aluminum on the porous structure. Figure 3 The X-ray diffraction pattern shows that, in addition to the characteristic peaks of CaCO3, Ca is clearly identifiable in the sample. a Al b O c The characteristic diffraction peaks indicate that the doped aluminum underwent a high-temperature solid-state reaction with the calcium-based component, generating calcium-aluminum composite oxides represented by Ca5(Al3O7)2. These composite oxides significantly increase the Taman temperature of the material and resist calcium carbonate sintering, serving as a key phase basis for maintaining the material's high-temperature cycling stability. Furthermore, due to the low cobalt doping level, no characteristic diffraction peaks attributable to cobalt were observed in the spectrum.

[0044] Tests showed that the specific surface area of ​​the composite particles was as high as 3.35 m². 2 / g, pore volume reaches 0.0094cm³ 3 / g; average spectral absorbance reaches 87.17%; average maximum compressive load reaches 6.79N; surface metallic Ni 0 It accounts for 31.58%. After undergoing 20 thermal cycles at 800℃, its energy storage density decay rate is only 17.05%.

[0045] Example 2

[0046] The calcium-nickel-based composite material for photothermal fluidized beds of the present invention, compared with Example 1, has a different molar ratio of metal elements (Ca:Al:Ni = 100:12:12), and its preparation method includes the following steps:

[0047] (1) Based on the molar ratio of metal elements Ca:Al:Ni = 100:12:12, weigh out the corresponding nickel nitrate and aluminum nitrate, and dissolve them thoroughly in deionized water to obtain a mixed solution; weigh out calcium hydroxide powder and microcrystalline cellulose, and dissolve them in water according to the ratio of 1 mol Ca... 2+ Mix the microcrystalline cellulose evenly according to the ratio of 15g, then add it to the above mixed solution and stir thoroughly to make a slurry.

[0048] (2) The obtained slurry is fed into an extruder and extruded to obtain a strip sample with a diameter of 0.4 mm. The strip sample is then fed into a spherical baller to form spherical particles and sieved.

[0049] (3) The sieved particles are transferred to a muffle furnace for calcination. The temperature is increased from room temperature to 500℃ at a rate of 2℃ / min and held for 2 hours. Then the temperature is increased to 800℃ at a rate of 2℃ / min and calcined for 1 hour.

[0050] (4) The calcined particles were placed in a tube furnace and reduced to 700°C for 2 hours at a heating rate of 10°C / min under a mixed atmosphere of 10 vol% H2 / Ar. Then the atmosphere was switched to pure CO2 for acidification treatment for 2 hours to obtain the calcium-nickel based composite material, denoted as Ca100Al12Ni12.

[0051] The specific surface area of ​​the composite particles was measured to be 2.68 m². 2 / g, pore volume is 0.0082cm³ 3 / g; average spectral absorbance reaches 87.88%; average maximum compressive load is 6.69N; surface metallic Ni 0 The proportion was 30.15%, and the conversion rate of CaO remained above 60% throughout 20 thermal cycles.

[0052] Example 3

[0053] The calcium-nickel-based composite material for photothermal fluidized beds of the present invention, compared with Example 1, has a different molar ratio of metal elements (Ca:Al:Ni = 100:10:12), and its preparation method includes the following steps:

[0054] (1) Based on the molar ratio of metal elements Ca:Al:Ni = 100:10:12, weigh out the corresponding nickel nitrate and aluminum nitrate, and dissolve them thoroughly in deionized water to obtain a mixed solution. Weigh out calcium hydroxide powder and microcrystalline cellulose, according to the ratio of 1 mol Ca... 2+ Mix the microcrystalline cellulose evenly according to the ratio of 15g, then add it to the above mixed solution and stir thoroughly to make a slurry.

[0055] (2) The obtained slurry is extruded to obtain strip-shaped samples with a diameter of 0.4 mm, which are then formed into spherical particles by a spherical rolling machine and sieved.

[0056] (3) Transfer the particles to a muffle furnace and heat them from room temperature to 500°C at a rate of 2°C / min and hold for 2 hours. Then heat them to 800°C at a rate of 2°C / min and calcine for 1 hour.

[0057] (4) Place the calcined granules in a tube furnace and heat them at 10 vol% H 2 Reduction was carried out at 700℃ for 2 hours under Ar atmosphere with a heating rate of 10℃ / min; then switched to pure CO. 2 The calcium-nickel-based composite material was obtained by acidification treatment for 2 hours, denoted as Ca100Al10Ni12.

[0058] The composite particles have a specific surface area of ​​2.25 m². 2 / g, pore volume is 0.0081cm³ 3 / g; average spectral absorbance is 85.89%; average maximum compressive load is 6.48N. After 20 thermal cycles, its average energy storage density is 1616.44 kJ / kg, and the energy storage density decay rate is 19.19%, demonstrating excellent anti-sintering performance.

[0059] To further highlight the comprehensive technical advantages of the calcium-nickel based composite material for photothermal fluidized beds provided by this invention in terms of mechanical compressive strength, high-temperature cycling stability, full-spectrum absorption, and intrinsic catalytic activity, and to verify the irreplaceable nature of the specific framework source component doping of this invention, the following comparative examples are set up for comparative analysis. The following comparative examples examine the performance of the unmodified pure calcium-based material of Comparative Example 1, the material of Comparative Example 2 with only physical pore formation, and the materials of Comparative Examples 3 and 4 with other common metal elements (magnesium, zinc) as framework sources.

[0060] Comparative Example 1

[0061] A pure calcium-based particulate material, compared with Example 1, Comparative Example 1 uses unmodified pure calcium-based material, and its preparation method includes the following steps:

[0062] (1) Without adding microcrystalline cellulose or any metal nitrates, simply weigh out calcium hydroxide powder, add an appropriate amount of deionized water, and stir thoroughly to make a slurry.

[0063] (2) The obtained slurry is extruded to obtain strip-shaped samples with a diameter of 0.4 mm, which are then formed into particles by a rounding machine and sieved;

[0064] (3) Place the particles in a muffle furnace, raise the temperature to 500°C at a rate of 2°C / min and hold for 2 hours, then raise the temperature to 800°C at a rate of 2°C / min and calcine for 1 hour.

[0065] (4) Place the calcined granules in a tube furnace and heat at 10 vol% H 2Reduction was carried out at 700℃ for 2 hours under an Ar atmosphere with a temperature increase of 10℃ / min; subsequently, reduction was carried out under pure CO. 2 After acidification treatment in an atmosphere for 2 hours, pure calcium-based particulate material was obtained, denoted as P-CaCO3.

[0066] The material exhibits a dense aggregated structure with a specific surface area of ​​only 0.68 m². 2 / g, pore volume is 0.0024cm³ 3 / g; the average spectral absorbance is extremely low, only 19.50%; the average maximum compressive load is only 0.82N. It is extremely prone to sintering and deactivation during thermal cycling, with a storage density decay rate as high as 45.68% after 20 cycles.

[0067] Comparative Example 2

[0068] A calcium-based particulate material containing only an organic pore-forming agent, compared to Example 1, and Comparative Example 2, which only involves physical pore formation, is prepared by the following steps:

[0069] (1) No metal nitrates are added. Weigh calcium hydroxide powder and microcrystalline cellulose, and mix them according to 1 mol Ca 2+ Mix the ingredients according to the ratio of 15g microcrystalline cellulose, add deionized water and stir thoroughly to make a slurry.

[0070] (2) The obtained slurry is extruded to obtain strip-shaped samples with a diameter of 0.4 mm, which are then formed into particles by a spheroidizing machine and sieved.

[0071] (3) Place the particles in a muffle furnace, raise the temperature to 500°C at a rate of 2°C / min and hold for 2 hours, then raise the temperature to 800°C at a rate of 2°C / min and calcine for 1 hour.

[0072] (4) The calcined particles were placed in a tube furnace and reduced to 700℃ for 2h at 10℃ / min under a 10 vol% H2 / Ar atmosphere; then acidified under a pure CO2 atmosphere for 2h to obtain the material, which was denoted as M-CaCO3.

[0073] After adding the pore-forming agent, the specific surface area of ​​the material increased to 1.26 m². 2 / g, pore volume 0.0069cm³ 3 / g, with an average spectral absorbance of 21.10%. However, due to the lack of inorganic framework support, the porosity disrupts the structural continuity, and its average maximum compressive load is reduced to 0.70N; the energy storage density decay rate after 20 cycles is as high as 51.11%.

[0074] Comparative Example 3

[0075] A magnesium-doped calcium-nickel-based composite material, compared with Example 1, Comparative Example 3 uses the common metal element magnesium as the framework source for doping, and its preparation method includes the following steps:

[0076] (1) Based on the molar ratio of metal elements Ca:Mg:Ni = 100:10:12, weigh out nickel nitrate and magnesium nitrate and dissolve them in deionized water. Weigh out calcium hydroxide powder and microcrystalline cellulose, and dissolve them in water according to the ratio of 1 mol Ca. 2+ Mix the ingredients according to the ratio of 15g microcrystalline cellulose, add the solution and stir to form a slurry.

[0077] (2) Extruded into strips with a diameter of 0.4 mm, rolled into granules and sieved.

[0078] (3) The temperature is raised to 500℃ at 2℃ / min and held for 2 hours, then raised to 800℃ and calcined for 1 hour.

[0079] (4) Reduced at 700℃ for 2h in a tubular furnace under a 10 vol% H2 / Ar atmosphere at 10℃ / min; then switched to pure CO2 acidification for 2h, and the resulting material was denoted as Ca100Mg10Ni12.

[0080] Material analysis showed that Mg doping produced Mg 0.03 Ca 0.97 With low-strength impurities such as CO3, the material's average maximum compressive load is only 0.80 N. Furthermore, the impurities solidify some visible light absorption sites, resulting in an average spectral absorbance of only 59.30%. The decay rate after 20 cycles is 23.46%.

[0081] Comparative Example 4

[0082] A zinc-doped calcium-nickel-based composite material, compared with Example 1, Comparative Example 4 uses the common metallic element zinc as the framework source for doping, and its preparation method includes the following steps:

[0083] (1) According to the molar ratio of metal elements Ca:Zn:Ni = 100:10:12, weigh out nickel nitrate and zinc nitrate and dissolve them in deionized water. Weigh out calcium hydroxide powder and microcrystalline cellulose, mix them at a ratio of 1 mol Ca2+ to 15 g microcrystalline cellulose, add them to the solution and stir to form a slurry.

[0084] (2) Extruded into strips with a diameter of 0.4 mm, rolled into granules and sieved.

[0085] (3) The temperature is raised to 500℃ at 2℃ / min and held for 2 hours, then raised to 800℃ and calcined for 1 hour.

[0086] (4) Reduced at 700℃ for 2h in a tubular furnace under a 10 vol% H2 / Ar atmosphere at 10℃ / min; then switched to pure CO2 acidification for 2h, and the resulting material was denoted as Ca100Zn10Ni12.

[0087] The material has an average spectral absorbance of 87.69% and an average maximum compressive load of 6.80 N. However, the doping of zinc in this system leads to a decrease in the proportion of effective energy storage components, resulting in the lowest initial energy storage density. Furthermore, the energy storage decays extremely drastically during 20 high-temperature cycles, with a decay rate as high as 49.63%.

[0088] The structures of the materials obtained in Examples 1-3 and Comparative Examples 1-4 in terms of various properties are shown in Table 1:

[0089] Table 1. Properties of materials prepared in the examples and comparative examples

[0090]

[0091] As shown in Table 1, the calcium-nickel based composite material provided by this invention achieves simultaneous and significant improvements in four dimensions: specific surface area, spectral absorbance, mechanical strength, and cycle stability. A comparison of Examples 1-3 with Comparative Examples 1-4 reveals that this difference in technical performance directly stems from the specific selection of the metal components and the optimization of their proportions in the technical solution.

[0092] Comparing Examples 1-3 with Comparative Examples 1 and 2, it can be seen that while physical pore creation (Comparative Example 2) can slightly increase the specific surface area, it leads to a decrease in the mechanical strength of the material (from 0.82 N to 0.70 N) and cannot improve the intrinsic defects of pure calcium-based materials, such as extremely low spectral absorption (approximately 19.50%) and poor thermal cycling stability (attenuation rate >45%). In contrast, this invention, through the synergistic doping of Al, Co, and Ni, not only constructs a well-developed porous network but also achieves a significant increase in strength (above 6.30 N) using a calcium aluminum oxide framework, and significantly enhances microwave absorption and anti-sintering properties.

[0093] The irreplaceability of the selected metal components in this application was further verified by comparing Examples 1-3 with Comparative Examples 3 and 4. Although magnesium doping in Comparative Example 3 has a pore-forming effect, the formation of a low-strength calcium magnesium carbonate impurity phase resulted in an average maximum compressive load of only 0.80 N, and the impurity phase solidified light absorption sites, reducing the absorptivity to only 59.30%. Although zinc doping in Comparative Example 4 maintained strength and absorptivity, its low proportion of effective energy storage components and lack of the skeletal barrier effect of aluminum resulted in a high energy density decay rate of 49.63% after 20 cycles. In contrast, Example 1 achieved a high absorptivity of 87.17%, a high strength of 6.79 N, and an extremely low decay rate of 17.05% while maintaining a high specific surface area of ​​3.35 m² / g, demonstrating the synergistic effect of the Al-Co-Ni multi-component system in maintaining the optimal overall performance of the material.

[0094] From the perspective of specific application areas, verifying the above performance indicators is of crucial significance for photothermal methane-calcium circulating dry reforming technology. In photothermal fluidized bed reactors, particles must undergo intense gas-solid turbulent motion. If the compressive load is insufficient, porous particles are easily pulverized and lost with the airflow. Therefore, high strength (>6 N) is a prerequisite for the engineering application of materials. At the same time, the system is directly driven by solar energy, and the high spectral absorptivity (>85%) directly determines the photothermal conversion efficiency and reaction rate. The large specific surface area provides abundant active sites for gas-solid multiphase catalytic reactions, while the low decay rate of the circulation performance ensures the economy of the heat storage medium in long-term continuous operation. This invention achieves synergistic improvement of various performances through multi-metal doping, precisely meeting the stringent requirements of photothermal fluidized beds for materials to have "high strength, high efficiency in microwave absorption, high stability, and strong mass transfer".

Claims

1. A calcium-nickel-based composite material for photothermal fluidized beds, characterized in that, The calcium-nickel-based composite material uses components including a calcium source, a framework source, a photothermal catalytic source, and a pore-forming agent as raw materials. Its structure has an interconnected microporous network formed by the pyrolysis of the pore-forming agent and is composited with an inorganic metal oxide framework doped with metal elements.

2. The calcium-nickel-based composite material for photothermal fluidized beds according to claim 1, characterized in that, The calcium source includes a calcium-containing compound, the photothermal catalytic source includes a nickel-containing compound, the framework source includes an aluminum-containing compound or a combination of an aluminum-containing compound and a cobalt-containing compound, the inorganic metal oxide framework is a calcium-aluminum composite oxide framework, and the molar ratio of each metal element is Ca:Al:Co:Ni = 100:5~15:0~5:8~15.

3. The calcium-nickel-based composite material for photothermal fluidized beds according to claim 2, characterized in that, The calcium-containing compound includes at least one of calcium hydroxide, calcium oxide, inorganic calcium salt, or organic calcium salt; the pore-forming agent is selected from at least one of cellulose, polysaccharide, polymer, or carbon-based material; the nickel-containing compound is selected from at least one of soluble inorganic nickel salt or organic nickel salt; the aluminum-containing compound is selected from at least one of soluble inorganic aluminum salt or organic aluminum salt; and the cobalt-containing compound is selected from at least one of soluble inorganic cobalt salt or organic cobalt salt.

4. The calcium-nickel-based composite material for photothermal fluidized beds according to claim 2, characterized in that, The calcium-containing compound is calcium hydroxide, the pore-forming agent is microcrystalline cellulose, the nickel-containing compound is nickel nitrate, the aluminum-containing compound is aluminum nitrate, and the cobalt-containing compound is cobalt nitrate.

5. A method for preparing a calcium-nickel-based composite material for photothermal fluidized beds as described in claim 1, characterized in that, It is prepared by extrusion-spheronization and calcination-reduction-acidification processes, including the following steps: (1) The photothermal catalyst source and the framework source are fully dissolved in a solvent to obtain a mixed solution. The calcium source and the pore-forming agent are mixed and added to the mixed solution and stirred thoroughly to obtain a slurry. (2) The slurry is extruded to obtain a strip sample, and then the strip sample is rolled into a spherical shape to obtain a granular mixture; (3) The granular mixture is calcined to pyrolyze the pore-forming agent and obtain calcined granules with a porous structure; (4) The calcined particles are subjected to reduction treatment and acidification treatment in sequence to obtain the calcium-nickel based composite material facing the photothermal fluidized bed.

6. The preparation method according to claim 5, characterized in that, In step (1), the solvent is water, and the mixing ratio of the calcium source and the pore-forming agent is: per 1 mol Ca 2+ Add 10-20g of pore-forming agent accordingly.

7. The preparation method according to claim 5, characterized in that, In step (3), the heating procedure for the calcination treatment is as follows: the temperature is raised from room temperature to 450-550℃ at a rate of 1-3℃ / min and held for 1-3 hours, and then raised to 750-850℃ at the same rate and calcined for 1-2 hours.

8. The preparation method according to claim 5, characterized in that, In step (4), the reduction treatment conditions are: under an atmosphere containing reducing gas, the temperature is increased to 650-750℃ for 1-3 hours at a heating rate of 5-15℃ / min; the acidification treatment conditions are: under an atmosphere containing acidic gas, the acidification treatment is carried out for 1-3 hours.

9. The preparation method according to claim 8, characterized in that, The atmosphere containing reducing gas is a reducing atmosphere containing H2, and the atmosphere containing acidic gas is a pure CO2 atmosphere.

10. The application of the calcium-nickel based composite material of claim 1 for photothermal fluidized beds in a photothermal methane calcium circulating dry reforming system or a calcium circulating carbon capture system.

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