A method for synthesizing a spherical nano calcium-based carbon dioxide adsorbent

Abstract

The present application relates to the field of calcium oxide synthesis, and discloses a method for synthesizing nanospherical calcium oxide carbon dioxide adsorbent.The method comprises the following steps: dissolving calcium nitrate and organic fuel in a solvent to prepare a precursor solution, wherein the solvent is deionized water or a mixture of deionized water and anhydrous ethanol; pressurizing the precursor solution and then feeding it into a pneumatic atomizing nozzle to form a precursor solution spray, and then feeding the precursor solution spray into a vertical tubular furnace to generate a combustion reaction, thereby obtaining nanospherical calcium oxide carbon dioxide adsorbent.The present application changes the form of the precursor solution by using a spray method, and further adjusts the size of the product particles by adjusting the usage ratio of the precursor raw materials, the reaction temperature and other methods, thereby obtaining nanospherical calcium-based carbon dioxide adsorbent with high carbon dioxide capture performance.

Description

Technical Field

[0001] This invention belongs to the technical field of calcium oxide synthesis, and more specifically, relates to a method for synthesizing nanosphere-shaped calcium oxide carbon dioxide adsorbent. Background Technology

[0002] Human activities have resulted in massive emissions of greenhouse gases, primarily CO2. The ever-increasing greenhouse effect is increasingly impacting the ecological environment, posing a growing threat to human survival and development. Therefore, CO2 emission reduction and control have become a major concern. Currently, coal consumption still accounts for over 50% of my country's energy structure; thus, reducing and controlling emissions from coal-fired power plants, the primary source of CO2 emissions, remains a key focus.

[0003] In the field of post-combustion CO2 capture technology, calcium recycling technology has attracted much attention due to its advantages such as low cost of adsorbent raw materials, high theoretical adsorption capacity, and fast reaction kinetics. Its basic principle is the reversible reaction of CaO with CO2 to produce CaCO3, and the reaction equation is as follows: ΔH = ±179 kJ / mol. The calcium cycle comprises two processes: carbonation and calcination. During carbonation (approximately 650°C), CaO reacts with CO2 in the flue gas to form CaCO3, thus capturing a low concentration of CO2. During calcination (approximately 850°C), CaCO3 decomposes, regenerating CaO and yielding high-purity CO2 for compression, storage, and utilization. The carbonation and calcination reactions occur cyclically, constituting the basic process of the calcium cycle.

[0004] However, calcium-based carbon dioxide adsorbents have several problems: First, the carbonation reaction of calcium oxide experiences a sudden, phased decrease in rate as the reaction progresses. This is because the CaCO3 product layer gradually accumulates on the CaO surface during carbonation, clogging the pores of the calcium-based adsorbent. CO2 must diffuse through the CaCO3 product layer to react with the internal CaO. Second, the CO2 capture capacity of calcium-based adsorbents decreases sharply with increasing carbonation / calcination cycles. This is because calcium-based adsorbents are prone to sintering after repeated high-temperature calcination, leading to CaO grain growth, pore blockage, and a rapid decrease in specific surface area and pore volume with increasing cycle number. Grasa et al. conducted carbonation / calcination experiments on natural limestone for up to 500 cycles and found that the carbonation conversion rate decreased from an initial 90% to a final 7-8%.

[0005] To address the problems associated with calcium-based adsorbents, the academic community has proposed various modification methods to improve their performance to varying degrees. These methods can be broadly categorized into three types: 1) Modifying natural calcium-based materials, such as high-temperature thermal pretreatment, steam activation, and organic acid modification; 2) Using special calcium precursors, such as nano-calcium carbonate precursors or organic calcium precursors; 3) Synthesizing novel calcium-based carbon dioxide adsorbents, such as sol-gel methods, flame spray pyrolysis, molecular self-assembly template methods, and hydrothermal methods. These methods are often used to add high-melting-point metal oxides (such as oxides of Mg, Al, Ti, Zr, and La) to calcium-based carbon dioxide adsorbents to obtain composite calcium-based adsorbents with better anti-sintering capabilities. Among these, metal oxides containing Mg and Al elements, such as MgO, Al2O3, Ca3Al2O6, and Ca... 12 Al 14 O 33 MgA l2 O4 and other similar substances are widely used in research due to their relatively low cost and ability to effectively improve the stability of cyclic CO2 capture performance of calcium-based carbon dioxide adsorbents. Among the three modification methods mentioned above, the third method can prepare nanoscale calcium-based carbon dioxide adsorbents with excellent performance. Taking the sol-gel method as an example, the CO2 capture capacity of the nanoscale calcium-based carbon dioxide adsorbent prepared by this method after 20 carbonation / calcination cycles is 1.5 to 2.5 times that of ordinary calcium oxide. However, most of the above-mentioned modification methods for preparing nanoscale calcium-based carbon dioxide adsorbents have complex preparation processes, harsh preparation conditions, long process cycles, and high costs, making it difficult to achieve industrial application in the short term. Therefore, proposing a synthesis method for nanoscale calcium-based carbon dioxide adsorbents with a simple preparation process, short preparation cycle, wide applicability, multiple adjustable parameters, strong controllability, and low requirements for industrial production equipment is of great significance for the application of calcium cycling technology. Summary of the Invention

[0006] In view of the above-mentioned defects or improvement needs of the existing technology, the purpose of this invention is to provide a method for synthesizing spherical nano-calcium-based carbon dioxide adsorbents. The method adopts a spray combustion method, changes the form of the precursor solution, and further adjusts the product particle size by combining the raw material ratio, reaction temperature and other methods, thereby obtaining spherical nano-calcium-based carbon dioxide adsorbents with high carbon dioxide capture performance.

[0007] To achieve the above objectives, according to a first aspect of the present invention, a method for synthesizing spherical nano-calcium-based carbon dioxide adsorbent is provided, comprising: dissolving calcium nitrate and organic fuel in a solvent to prepare a precursor solution, wherein the solvent is deionized water or a mixture of deionized water and anhydrous ethanol; pressurizing the precursor solution and passing it through a pneumatic atomizing nozzle to form a precursor solution spray, and then entering a vertical tube furnace to undergo a combustion reaction to obtain nano-spherical calcium oxide carbon dioxide adsorbent.

[0008] As a preferred embodiment of the present invention, the flow rate of the precursor solution after pressurization is 5-50 mL / min;

[0009] The flow rate of compressed air in the pneumatic atomizing nozzle is 10-50 L / min.

[0010] As a preferred embodiment of the present invention, the size of the precursor solution spray is 0.1 to 15 μm.

[0011] As a preferred embodiment of the present invention, the molar ratio of the organic fuel to the calcium nitrate is (0.2-3):1, preferably (0.5-1.5):1.

[0012] As a preferred embodiment of the present invention, the organic fuel includes at least one of a class of substances, namely organic acids or sugars, or a combination of at least one of organic acids and at least one of sugars.

[0013] The organic acids include acetic acid, propionic acid, lactic acid, citric acid, malic acid, tartaric acid, or glycine; the sugars include glucose or fructose.

[0014] As a preferred embodiment of the present invention, the precursor solution further comprises a metal nitrate that can decompose to form a high-melting-point metal oxide, wherein the high-melting-point metal oxide has a melting point greater than 1600°C.

[0015] The molar ratio of the metal nitrate that can decompose to form a high-melting-point metal oxide to the calcium nitrate is (0-0.4):1, preferably (0.1-0.2):1.

[0016] As a preferred embodiment of the present invention, the molar ratio of anhydrous ethanol to deionized water is (0.1-3):1;

[0017] The molar ratio of the solvent to the calcium nitrate is (10-40):1.

[0018] As a preferred embodiment of the present invention, the temperature of the vertical tube furnace is 500-1000°C, preferably 600-900°C, and combustion occurs inside the vertical tube furnace.

[0019] As an embodiment of the present invention, the vertical tube furnace has a tube length of 1000-2000 mm and an inner diameter of 100-400 mm.

[0020] According to another aspect of the present invention, a nanosphere calcium oxide carbon dioxide adsorbent is prepared by the method described in any of the first aspects.

[0021] In summary, compared with the prior art, the above-described technical solutions conceived by this invention mainly possess the following technical advantages:

[0022] (1) The present invention adopts the spray combustion method. After calcium nitrate and organic fuel are prepared into a precursor solution, the precursor solution is atomized into a spray with tiny droplets by using a pneumatic atomizing nozzle. The size of the product particles can be adjusted by further adjusting the ratio of raw materials and reaction temperature, thereby obtaining a spherical nano-calcium-based carbon dioxide adsorbent with high carbon dioxide capture performance.

[0023] Furthermore, compared to the ultrasonic atomizing device commonly used in existing technologies as the source of micro-droplets, the pneumatic atomizing nozzle used in the preparation method of this invention is suitable for a wider variety of precursor raw materials and precursor solutions with higher viscosity, and is easy to industrialize, enabling higher nanoparticle yields. In addition, compared to the flame spray pyrolysis method commonly used in existing technologies for nanoparticle synthesis, the preparation method of this invention does not require the use of premixed flames containing gases such as CH4 and H2 as the energy source for particle synthesis. Instead, it employs a stable high-temperature reaction environment, relying on the combustion of organic fuels in the precursor solution to provide energy for particle synthesis. This avoids the risk of flammable gas leakage during synthesis, improving the safety of the preparation process. It also avoids the problem of particle hollowing caused by excessively high flame edge temperature gradients when using premixed flames containing gases such as CH4 and H2 for particle synthesis.

[0024] (2) The method proposed in this invention can adjust the size of the product particles by changing the type of organic fuel in the precursor solution and the ratio of organic fuel to calcium nitrate, the flow rate of the compressed precursor solution, the flow rate of compressed air, and the reaction temperature, thereby obtaining spherical nano-calcium-based carbon dioxide adsorbents with high carbon dioxide capture performance. In addition, by changing the ratio of calcium nitrate to other metal nitrates, the ratio of CaO to anti-sintering metal oxides in the final prepared spherical nano-calcium-based carbon dioxide adsorbent can be controlled, thereby controlling the stability of the cyclic CO2 capture performance of the spherical nano-calcium-based carbon dioxide adsorbent. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the process for synthesizing spherical nano-calcium-based carbon dioxide adsorbents according to an example of the present invention;

[0026] Figure 2 The XRD pattern of the spherical nano-calcium-based carbon dioxide adsorbent exemplified in Example 1 of this invention;

[0027] Figure 3 This is a TEM image of the spherical nano-calcium-based carbon dioxide adsorbent exemplified in Example 1 of the present invention; Figure 3 The scale bars in ac are 0.5μm, 200nm, and 100nm, respectively;

[0028] Figure 4 The results of the cyclic CO2 capture performance test of the spherical nano-calcium-based carbon dioxide adsorbent exemplified in Example 1 of the present invention are shown.

[0029] Figure 5 The XRD pattern of the spherical nano-calcium-based carbon dioxide adsorbent of Example 2 of the present invention is shown below.

[0030] Figure 6 This is a TEM image of the spherical calcium nanoparticle-based carbon dioxide adsorbent exemplified in Example 2 of the present invention; Figure 6 The scale bars in ac are 0.5μm, 200nm, and 100nm, respectively;

[0031] Figure 7 The results of the cyclic CO2 capture performance test of the spherical nano-calcium-based carbon dioxide adsorbent in Example 2 of this invention are shown.

[0032] Figure 8 The XRD pattern of the spherical nano-calcium-based carbon dioxide adsorbent exemplified in Example 3 of the present invention is shown below.

[0033] Figure 9 This is a TEM image of the spherical nano-calcium-based carbon dioxide adsorbent exemplified in Example 3 of the present invention; Figure 9 The scale bars in ac are 0.5μm, 200nm, and 100nm, respectively;

[0034] Figure 10 The results of the cyclic CO2 capture performance test of the spherical nano-calcium-based carbon dioxide adsorbent exemplified in Example 3 of the present invention are shown.

[0035] Figure 11 This is a TEM image of the spherical calcium nanoparticle-based carbon dioxide adsorbent exemplified in Example 4 of the present invention; Figure 11 The scale bars in ac are 0.5μm, 200nm, and 100nm, respectively;

[0036] Figure 12 The results of the cyclic CO2 capture performance test of the spherical nano-calcium-based carbon dioxide adsorbent in Example 4 of this invention are shown.

[0037] Figure 13The image shows a TEM image of the spherical nano-calcium-based carbon dioxide adsorbent of Comparative Example 1 of the present invention. Figure 13 The scale bars for 'a' and 'b' in the diagram are 0.5 μm.

[0038] Figure 14 The results of the cyclic CO2 capture performance test of the spherical nano-calcium-based carbon dioxide adsorbent of Comparative Example 1 of the present invention are shown.

[0039] Figure 15 The image shows a TEM image of the spherical nano-calcium-based carbon dioxide adsorbent of Comparative Example 2 of the present invention. Figure 15 The scale bars in ac are 0.5μm, 0.2μm, and 100nm, respectively;

[0040] Figure 16 The results show the cyclic CO2 capture performance test results of the spherical nano-calcium-based carbon dioxide adsorbent of Comparative Example 2 of the present invention. Detailed Implementation

[0041] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0042] In embodiments of the present invention, such as Figure 1 As shown, a method for synthesizing spherical nano-calcium-based carbon dioxide adsorbents by spray combustion is provided, comprising the following steps:

[0043] (1) Prepare a precursor solution by dissolving calcium nitrate and organic fuel in deionized water or a mixture of deionized water and anhydrous ethanol. Alternatively, the precursor solution may also contain other metal nitrates.

[0044] (2) The precursor solution is fed into the liquid inlet of the pneumatic atomizing nozzle through a liquid booster pump. The liquid outlet opening of the pneumatic atomizing nozzle is adjusted to achieve a specific liquid flow rate to form a stable liquid column.

[0045] Turn on the air compressor to introduce compressed air into the gas inlet of the pneumatic atomizing nozzle. Adjust the gas outlet opening of the pneumatic atomizing nozzle to achieve a specific gas flow rate. Under the shear force of the compressed air, the liquid column is atomized to form a stable precursor solution spray.

[0046] (3) The droplet cluster (i.e., the precursor solution spray) enters a high-temperature vertical tube furnace under the action of compressed air and undergoes a violent combustion reaction. The powder product is collected at the end of the vertical tube furnace, washed with anhydrous ethanol to remove impurities, filtered, and then vacuum dried to obtain the final product, spherical nano-calcium-based carbon dioxide adsorbent.

[0047] In some embodiments, the precursor solution further includes anhydrous ethanol as a combustion improver for the organic fuel. When anhydrous ethanol is included, anhydrous ethanol and deionized water are used as solvents in the precursor solution, and the molar ratio of anhydrous ethanol to deionized water is (0.1–3):1.

[0048] When using deionized water or a mixture of deionized water and anhydrous ethanol as a solvent, the molar ratio of the solvent to calcium nitrate is (10-40):1.

[0049] In some embodiments, the molar ratio of organic fuel to calcium nitrate is (0.2–3):1, preferably (0.5–1.5):1.

[0050] Organic fuels include at least one of the following classes of substances: organic acids or sugars, or a combination of at least one organic acid and at least one sugar.

[0051] Among them, organic acids include acetic acid, propionic acid, lactic acid, citric acid, malic acid, tartaric acid, or glycine; sugars are glucose or fructose.

[0052] In some embodiments, the precursor solution further comprises a metal nitrate that can decompose to form a high-melting-point metal oxide, wherein the high-melting-point metal oxide has a melting point greater than 1600°C. Examples include nitrates formed from nitrates of elements such as Mg, Al, La, Zr, Y, Ce, and Fe.

[0053] The molar ratio of the metal nitrate that can decompose to form a high-melting-point metal oxide to the calcium nitrate is (0-0.4):1, preferably (0.1-0.2):1.

[0054] Among them, metal nitrates that can decompose to form metal oxides with high melting points include one or a mixture of two of magnesium nitrate, aluminum nitrate, lanthanum nitrate, zirconium nitrate, yttrium nitrate, cerium nitrate, or iron nitrate.

[0055] In some embodiments, the precursor solution is pressurized to 0.02–0.2 MPa using a liquid booster pump and then introduced into the liquid inlet of a pneumatic atomizing nozzle. The liquid outlet opening of the pneumatic atomizing nozzle is adjusted to achieve a specific liquid flow rate, forming a stable liquid column. This results in a flow rate of 5–50 mL / min for the pressurized precursor solution (i.e., the aforementioned stable liquid column).

[0056] In some embodiments, the air compressor is turned on to generate compressed air with a pressure of 0.1 to 0.5 MPa, such that the flow rate of the compressed air is in the range of 10 to 50 L / min.

[0057] In some embodiments, under the different precursor formulations described above, the flow rate of the pressurized precursor solution and the flow rate of compressed air are adjusted, and the size of the ultrafine precursor solution spray formed after being introduced into the pneumatic atomizing nozzle is 0.1 to 15 μm.

[0058] In some embodiments, the temperature of the vertical tube furnace is 500–1000°C, preferably 600–900°C, and combustion occurs inside the vertical tube furnace.

[0059] In some embodiments, the vertical tube furnace has a tube length of 1000-2000 mm and an inner diameter of 100-400 mm.

[0060] In a subsequent specific embodiment, the quartz tube used in the vertical tube furnace has an outer diameter of 300 mm, an inner diameter of 288 mm, and a length of 1400 mm. When the spray enters the quartz tube of the tube furnace, which has reached the reaction temperature, the water on the outer surface of the droplets first evaporates due to heat, causing the droplets to shrink. This results in a higher concentration of the solution on the outer surface of the droplets compared to the internal solution. Under the high-temperature environment provided by the vertical tube furnace, the external temperature of the droplets reaches the combustion temperature of the organic fuel, leading to violent combustion and the generation of a large amount of gas. The main reaction equation is: Ca(NO3)2 + C x H y O z →CaO + CO2 + H2O + N2 and M(NO3) n +C x H y O z →MO + CO2 + H2O + N2, where C x H y O z Depending on the type of organic fuel used in the preparation process, M(NO3) n It is a metal nitrate that can decompose at high temperatures to form metal oxides with high melting points. During this process, the droplets "explode" to form multiple submicron-sized microdroplets, and each microdroplet undergoes solute deposition, crystallization, and sintering agglomeration, ultimately forming a spherical nanoscale calcium-based carbon dioxide adsorbent.

[0061] The nanoscale calcium-based carbon dioxide adsorbent prepared by the above embodiments of the present invention is spherical with a rough surface and an average size between 10 and 100 nm.

[0062] The specific test based on the embodiments of the present invention is as follows:

[0063] Physicochemical property characterization of the samples: The average particle size of the precursor solution spray was characterized by a laser particle size analyzer; the phase composition of the calcium-based carbon dioxide adsorbent samples was characterized by X-ray diffraction (XRD); the microstructure of the calcium-based carbon dioxide adsorbent samples was characterized by transmission electron microscopy (TEM); and the circulating CO2 capture performance of the calcium-based carbon dioxide adsorbent samples was tested by a synchronous thermal analyzer (STA).

[0064] Laser particle size analyzer testing: A PW180-B spray laser particle size analyzer manufactured by Niket Analytical Instruments Co., Ltd. was used. The laser wavelength was 635nm and the power was 20mW. The horizontal plane of the laser was 0.2m above the outlet of the pneumatic atomizing nozzle. The measurement time for each set of data was 60s. The Sothel average particle size (D) was calculated. 32 The average particle size of the precursor solution spray is characterized by the formula D. 32 =(ΣND 3 ) / ND 2 , where N is the number of droplets with diameter D.

[0065] The CO2 capture performance of the samples was characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), surface area analyzer, and simultaneous thermal analyzer (STA).

[0066] X-ray diffraction analysis: An Empyrean X-ray diffractometer manufactured by PANalytical BV, Netherlands, was used. A Cu target Kα1 was used, the incident light wavelength λ = 0.15406 nm, the tube voltage was 40 kV, the tube current was 40 mA, the scanning diffraction angle 2θ ranged from 5 to 90°, and the scanning speed was 0.05° / min.

[0067] Transmission electron microscopy analysis: A Tecnai G2 20 transmission electron microscope manufactured by FEI (Netherlands) was used. Before observation, the sample was ultrasonically dispersed in anhydrous ethanol, and the supernatant was dropped onto a copper grid and then dried under an infrared lamp to remove the anhydrous ethanol.

[0068] CO2 capture performance testing: A simultaneous thermal analyzer STA 2500Regulus manufactured by NETZSCH GmbH, Germany, was used. For each test, approximately 3 mg of calcium-based carbon dioxide adsorbent sample was placed in an alumina crucible, and the test was conducted according to the following procedure: First, the sample was pre-calcined in a N2 atmosphere at a rate of 100 ml / min: the temperature was increased from 20°C to 850°C at a rate of 30°C / min and held constant for 20 min to ensure complete decomposition of residual Ca(OH)2 and CaCO3 in the sample. Subsequently, the temperature was decreased to 650°C at a rate of 30°C / min. At 650°C, the atmosphere was adjusted to a CO2 capture rate of 15 ml / min. 2+ Carbonation was performed using 85 ml / min N2 for 10 min. After carbonation, the atmosphere was adjusted to 100 ml / min N2, and the temperature was increased to 850°C at a rate of 30°C / min to enter the calcination stage, which was held at that temperature for 10 min to complete the decomposition of CaCO3 and the regeneration of CaO in the calcium-based carbon dioxide adsorbent. Each cycle consisted of one carbonation stage and one calcination stage. The CO2 capture performance test for each sample was repeated 25 times. Additionally, analytical grade CaCO3 was used for cycle performance testing under the same conditions as a comparison; the results were recorded as ordinary CaO.

[0069] Some specific embodiments will be given below, along with detailed descriptions in conjunction with the accompanying drawings.

[0070] Example 1:

[0071] Measure 1 mol of calcium nitrate, 1 mol of citric acid, and 0.1 mol of magnesium nitrate into a container, add 10 mol of deionized water to fully dissolve and mix the calcium nitrate, citric acid, and magnesium nitrate to prepare a precursor solution.

[0072] The pressure of the precursor solution is increased to 0.1 MPa by a liquid booster pump and then introduced into the liquid inlet of the pneumatic atomizing nozzle. The liquid outlet opening of the pneumatic atomizing nozzle is adjusted to achieve a liquid flow rate of 20 mL / min, forming a stable liquid column.

[0073] An air compressor was turned on to generate compressed air at a pressure of 0.2 MPa. This compressed air was then introduced into the gas inlet of a pneumatic atomizing nozzle. The gas outlet opening of the nozzle was adjusted to achieve a gas flow rate of 25 L / min. Under the shear force of the compressed air, the liquid column was atomized, forming a stable, ultra-fine spray. The Sothel average particle size of the precursor solution spray was determined to be 8.5 μm using a laser particle size analyzer. The droplet group then entered a high-temperature vertical tube furnace at 700 °C under the action of compressed air, where a vigorous combustion reaction occurred. The powder product was collected at the end of the furnace, washed with anhydrous ethanol to remove impurities, filtered, and then vacuum dried to obtain the final product: spherical nano-calcium-based carbon dioxide adsorbent.

[0074] Figure 2 The XRD pattern of the spherical calcium nanoparticle-based carbon dioxide adsorbent prepared in Example 1 is shown. It can be seen that the characteristic peak corresponding to CaO has the highest peak intensity, indicating that CaO is the most dominant phase in the spherical calcium nanoparticle-based carbon dioxide adsorbent prepared in Example 1. In addition, characteristic peaks of Ca(OH)2 and MgO with lower intensities can also be identified in the XRD pattern. The presence of trace amounts of Ca(OH)2 is due to the extremely strong reactivity and water absorption properties of nano-sized CaO, causing it to react with water vapor in the air during the sample preparation stage before XRD testing. Furthermore, the presence of MgO indicates that magnesium nitrate in the precursor solution is converted to MgO during the spray combustion process. This metal oxide can serve as an inert metal oxide to enhance the anti-sintering ability of the spherical calcium nanoparticle-based carbon dioxide adsorbent, thereby improving the stability of the circulating CO2 capture performance.

[0075] Figure 3 These are TEM images of the spherical calcium-based nanoparticles of carbon dioxide adsorbent prepared in Example 1 of this invention. Figure 3 Images a, b, and c in the image are shown at different magnifications, with scale bars of 0.5 μm, 200 nm, and 100 nm, respectively. This demonstrates that the method described in Example 1 can successfully prepare nanoscale particles with uniform particle size distribution and good sphericity. The average particle size was calculated to be 63 nm by statistically analyzing the diameters of 20 different spherical calcium-based carbon dioxide adsorbent nanoparticles in the TEM images.

[0076] Figure 4The figure shows the cyclic CO2 capture performance curves of the spherical nano-calcium-based carbon dioxide adsorbent prepared in Example 1. The performance curves of ordinary CaO under the same test conditions are also shown. Ordinary CaO, due to severe sintering during multiple carbonation-calcination cycles, experienced a decrease in its CO2 adsorption capacity from 0.663 g CO2 / g adsorbent in the first cycle to 0.177 g CO2 / g adsorbent in the 25th cycle, representing a performance degradation rate of 73.3% from the first to the 25th cycle. In contrast, the spherical nano-calcium-based carbon dioxide adsorbent prepared in Example 1 exhibited an adsorption capacity of 0.715 g CO2 / g adsorbent in the first cycle and 0.571 g CO2 / g adsorbent in the 25th cycle, representing a performance degradation rate of 20% from the first to the 25th cycle. The spherical nano-calcium-based carbon dioxide adsorbent prepared in Example 1 showed a 7.8% increase in adsorption capacity in the first cycle and a 222.6% increase in adsorption capacity in the 25th cycle compared to ordinary CaO. The CO2 capture performance stability from the first cycle to the 25th cycle was improved by 72.7%.

[0077] Example 2:

[0078] Measure 1 mol of calcium nitrate, 0.5 mol of glycine, and 0.2 mol of aluminum nitrate into a container. Add a mixture containing 10 mol of deionized water and 10 mol of anhydrous ethanol to fully dissolve and mix the calcium nitrate, glycine, and aluminum nitrate to prepare a precursor solution.

[0079] The precursor solution was pressurized to 0.15 MPa using a liquid booster pump and then introduced into the liquid inlet of a pneumatic atomizing nozzle. The liquid outlet opening of the nozzle was adjusted to achieve a flow rate of 30 mL / min, forming a stable liquid column. An air compressor was then activated to generate compressed air at 0.1 MPa. This compressed air was introduced into the gas inlet of the atomizing nozzle, and the gas outlet opening was adjusted to achieve a flow rate of 20 L / min. Under the shear force of the compressed air, the liquid column was atomized, forming a stable, extremely fine spray. The Sothel average particle size of the precursor solution spray was determined to be 10.4 μm using a laser particle size analyzer. The droplet group, under the action of compressed air, entered a high-temperature vertical tube furnace at 900℃, where a vigorous combustion reaction occurred. The powder product was collected at the end of the furnace, washed with anhydrous ethanol to remove impurities, filtered, and then vacuum dried to obtain the final product: spherical nano-calcium-based carbon dioxide adsorbent.

[0080] Figure 5The XRD pattern of the spherical calcium nanoparticle-based carbon dioxide adsorbent prepared in Example 2 is shown below. First, the characteristic peak corresponding to CaO has the highest intensity, indicating that CaO is the dominant phase in the spherical calcium nanoparticle-based carbon dioxide adsorbent prepared in Example 2. Second, a characteristic peak of Ca(OH)2 with a lower intensity can also be identified in the XRD pattern, proving the presence of trace amounts of Ca(OH)2 in the test sample. The presence of this phase is due to the extremely strong reactivity and water absorption properties of nano-sized CaO, which caused it to react with water vapor in the air during the sample preparation stage before XRD testing. Additionally, a high-intensity Ca3A peak can also be identified in the XRD pattern. l2 The characteristic peak corresponding to O6 and the low intensity of Ca 12 Al 14 O 33 The corresponding characteristic peaks prove that after the spray combustion process, aluminum nitrate and calcium nitrate in the precursor solution react to form Ca3Al2O6 with a relatively high content and Ca with a relatively low content. 12 Al 14 O 33 Both of these metal oxides can be used as inert metal oxides to enhance the anti-sintering ability of spherical nano-calcium-based carbon dioxide adsorbents, thereby improving the stability of cyclic CO2 capture performance.

[0081] Figure 6 These are TEM images of the spherical calcium-based carbon dioxide adsorbent nanoparticles prepared in this embodiment. Figure 6 Images a, b, and c in the image are of this sample at different magnifications, with scale bars of 0.5 μm, 200 nm, and 100 nm, respectively. It can be seen that nanoscale particles with uniform particle size distribution and good sphericity can be successfully prepared using Example 2. The average particle size was calculated to be 95 nm by statistically analyzing the diameters of 20 different spherical calcium-based carbon dioxide adsorbent nanoparticles in the TEM images.

[0082] Figure 7The figure shows the cyclic CO2 capture performance curves of the spherical nano-calcium-based carbon dioxide adsorbent prepared in Example 2. The performance curves of ordinary CaO under the same test conditions are also shown. Ordinary CaO, due to severe sintering during multiple carbonation-calcination cycles, experienced a decrease in its CO2 adsorption capacity from 0.663 g CO2 / g adsorbent in cycle 1 to 0.361 g CO2 / g adsorbent in cycle 5, and finally further decreased to 0.177 g CO2 / g adsorbent in cycle 25, representing a performance degradation rate of 51% from cycle 5 to cycle 25. In contrast, the spherical nano-calcium-based carbon dioxide adsorbent prepared in Example 2 exhibited an adsorption capacity of 0.57 g CO2 / g adsorbent in cycle 1, 0.591 g CO2 / g adsorbent in cycle 5, and 0.583 g CO2 / g adsorbent in cycle 25, representing a performance degradation rate of 1.4% from cycle 5 to cycle 25. The spherical nano-calcium-based carbon dioxide adsorbent prepared in Example 2 showed a 63.7% increase in adsorption capacity in the 5th cycle and a 229.4% increase in adsorption capacity in the 25th cycle compared to ordinary CaO. The CO2 capture performance stability from the 5th to the 25th cycle was improved by 97.3%.

[0083] Example 3:

[0084] Measure 1 mol of calcium nitrate, 2 mol of glucose, 0.2 mol of magnesium nitrate and 0.2 mol of aluminum nitrate into a container, add a mixture containing 20 mol of deionized water and 10 mol of anhydrous ethanol to fully dissolve and mix the calcium nitrate, glucose, magnesium nitrate and aluminum nitrate to prepare a precursor solution.

[0085] The precursor solution was pressurized to 0.05 MPa using a liquid booster pump and then introduced into the liquid inlet of a pneumatic atomizing nozzle. The liquid outlet opening of the nozzle was adjusted to achieve a flow rate of 15 mL / min, forming a stable liquid column. An air compressor was then activated to generate compressed air at 0.4 MPa. This compressed air was then introduced into the gas inlet of the atomizing nozzle, and the gas outlet opening was adjusted to achieve a flow rate of 35 L / min. Under the shear force of the compressed air, the liquid column was atomized, forming a stable, ultra-fine spray. The Sothel average particle size of the precursor solution spray was determined to be 4.9 μm using a laser particle size analyzer. The droplet group, under the action of compressed air, entered a high-temperature vertical tube furnace at 800℃, where a vigorous combustion reaction occurred. The powder product was collected at the end of the furnace, washed with anhydrous ethanol to remove impurities, filtered, and then vacuum dried to obtain the final product: spherical nano-calcium-based carbon dioxide adsorbent.

[0086] Figure 8The XRD pattern of the spherical calcium nanoparticle-based carbon dioxide adsorbent prepared in Example 3 is shown below. First, the characteristic peak corresponding to CaO has the highest intensity, indicating that CaO is the dominant phase in the spherical calcium nanoparticle-based carbon dioxide adsorbent prepared in this example. Second, a low-intensity characteristic peak of Ca(OH)2 can also be identified in the XRD pattern, proving the presence of trace amounts of Ca(OH)2 in the test sample. The presence of this phase is due to the extremely strong reactivity and water absorption properties of nano-sized CaO, causing it to react with water vapor in the air during the sample preparation stage before XRD testing. Furthermore, a high-intensity characteristic peak corresponding to MgAl2O4 can also be identified in the XRD pattern, proving that after the spray combustion process, aluminum nitrate and magnesium nitrate in the precursor solution react to form a relatively high content of MgAl2O4. These metal oxides can serve as inert metal oxides to enhance the anti-sintering ability of the spherical calcium nanoparticle-based carbon dioxide adsorbent, thereby improving the stability of the circulating CO2 capture performance.

[0087] Figure 9 These are TEM images of the spherical calcium-based carbon dioxide adsorbent nanoparticles prepared in this embodiment. Images a, b, and c in example 9 are images of this sample at different magnifications, with scale bars of 0.5 μm, 200 nm, and 100 nm, respectively. It is evident that this embodiment 3 successfully prepared nanoscale particles with uniform particle size distribution and good sphericity. The average particle size was calculated to be 45 nm by statistically analyzing the diameters of 20 different spherical calcium-based carbon dioxide adsorbent nanoparticles in the TEM images.

[0088] Figure 10 The figure shows the cyclic CO2 capture performance curves of the spherical nano-calcium-based carbon dioxide adsorbent prepared in Example 3. The performance curves of ordinary CaO under the same test conditions are also shown. Ordinary CaO, due to severe sintering during multiple carbonation-calcination cycles, experienced a decrease in its CO2 adsorption capacity from 0.663 g CO2 / g adsorbent in the first cycle to 0.177 g CO2 / g adsorbent in the 25th cycle, representing a performance degradation rate of 73.3% from the first to the 25th cycle. In contrast, the spherical nano-calcium-based carbon dioxide adsorbent prepared in Example 3 exhibited an adsorption capacity of 0.59 g CO2 / g adsorbent in the first cycle and 0.545 g CO2 / g adsorbent in the 25th cycle, representing a performance degradation rate of 7.6% from the first to the 25th cycle. The spherical nano-calcium-based carbon dioxide adsorbent prepared in Example 3 showed an 11% increase in adsorption capacity in the first cycle and a 207.9% increase in adsorption capacity in the 25th cycle compared to ordinary CaO. The stability of CO2 capture performance from the first cycle to the 25th cycle was improved by 89.6%.

[0089] Example 4:

[0090] Measure 1 mol of calcium nitrate, 0.5 mol of glycine, and 0.2 mol of aluminum nitrate into a container. Add a mixture containing 10 mol of deionized water and 10 mol of anhydrous ethanol to fully dissolve and mix the calcium nitrate, glycine, and aluminum nitrate to prepare a precursor solution.

[0091] The precursor solution was pressurized to 0.15 MPa using a liquid booster pump and then introduced into the liquid inlet of a pneumatic atomizing nozzle. The liquid outlet opening of the nozzle was adjusted to achieve a flow rate of 20 mL / min, forming a stable liquid column. An air compressor was then activated to generate compressed air at 0.1 MPa. This compressed air was then introduced into the gas inlet of the atomizing nozzle, and the gas outlet opening was adjusted to achieve a flow rate of 30 L / min. Under the shear force of the compressed air, the liquid column was atomized, forming a stable, extremely fine spray. The Sothel average particle size of the precursor solution spray was determined to be 7.6 μm using a laser particle size analyzer. The droplet group then entered a high-temperature vertical tube furnace at 700°C under the action of compressed air, where a vigorous combustion reaction occurred. The powder product was collected at the end of the furnace, washed with anhydrous ethanol to remove impurities, filtered, and then vacuum dried to obtain the final product: spherical nano-calcium-based carbon dioxide adsorbent.

[0092] Figure 11 These are TEM images of the spherical calcium nanoparticle-based carbon dioxide adsorbent prepared in Example 4. Figure 13 Images a, b, and c in the image are of this sample at different magnifications, with scale bars of 0.5 μm, 200 nm, and 50 nm, respectively. This demonstrates that nanoscale particles with uniform particle size distribution and good sphericity can be successfully prepared using Example 4. The average particle size was calculated to be 75 nm by statistically analyzing the diameters of 20 different spherical calcium-based carbon dioxide adsorbent nanoparticles in the TEM images.

[0093] Figure 12The figure shows the cyclic CO2 capture performance curves of the spherical calcium nanoparticle-based carbon dioxide adsorbent prepared in Example 4. The performance curves of ordinary CaO under the same test conditions are also shown. Ordinary CaO, due to severe sintering during multiple carbonation-calcination cycles, experienced a decrease in its CO2 adsorption capacity from 0.663 g CO2 / g adsorbent in the first cycle to 0.439 g CO2 / g adsorbent in the third cycle, and finally further decreased to 0.177 g CO2 / g adsorbent in the 25th cycle, representing a performance degradation rate of 59.7% from the third to the 25th cycle. In contrast, the spherical calcium nanoparticle-based carbon dioxide adsorbent prepared in Example 4 exhibited an adsorption capacity of 0.649 g CO2 / g adsorbent in the first cycle, 0.607 g CO2 / g adsorbent in the third cycle, and 0.598 g CO2 / g adsorbent in the 25th cycle, representing a performance degradation rate of 1.5% from the third to the 25th cycle. The spherical nano-calcium-based carbon dioxide adsorbent prepared by the method in Example 4 showed a 38.3% increase in adsorption capacity in the 3rd cycle and a 237.9% increase in adsorption capacity in the 25th cycle compared to ordinary CaO. The stability of CO2 capture performance from the 1st to the 25th cycle was improved by 89.2%.

[0094] Comparative Example 1:

[0095] Measure 1 mol of calcium nitrate, 0.5 mol of glycine, and 0.2 mol of aluminum nitrate into a container. Add a mixture containing 10 mol of deionized water and 10 mol of anhydrous ethanol to fully dissolve and mix the calcium nitrate, glycine, and aluminum nitrate to prepare a precursor solution.

[0096] The precursor solution was pressurized to 0.2 MPa using a liquid booster pump and then introduced into the liquid inlet of a pneumatic atomizing nozzle. The liquid outlet opening of the nozzle was adjusted to achieve a flow rate of 100 mL / min, forming a stable liquid column. An air compressor was then activated to generate compressed air at 0.4 MPa. This compressed air was introduced into the gas inlet of the atomizing nozzle, and the gas outlet opening was adjusted to achieve a flow rate of 60 L / min. Under the shear force of the compressed air, the liquid column was atomized, forming a stable, extremely fine spray. The Sothel average particle size of the precursor solution spray was determined to be 20.6 μm using a laser particle size analyzer. The droplet group then entered a high-temperature vertical tube furnace at 900°C under the action of compressed air, where a vigorous combustion reaction occurred. The powder product was collected at the end of the furnace, washed with anhydrous ethanol to remove impurities, filtered, and then vacuum dried to obtain the final product: spherical nano-calcium-based carbon dioxide adsorbent.

[0097] Figure 13The images show TEM images of the spherical calcium-based carbon dioxide adsorbent nanoparticles prepared in Comparative Example 1. The scale bars in the images are all 0.5 μm. It is evident that the method described in Comparative Example 1 cannot successfully prepare nanoscale particles with uniform particle size distribution and good sphericity; therefore, it is impossible to statistically analyze the average particle size.

[0098] Figure 14 The figure shows the cyclic CO2 capture performance curves of the calcium-based carbon dioxide adsorbent prepared in Comparative Example 1. The performance curves of ordinary CaO under the same test conditions are also shown. Ordinary CaO, due to severe sintering during multiple carbonation-calcination cycles, experienced a decrease in CO2 adsorption capacity from 0.663 g CO2 / g adsorbent in cycle 1 to 0.361 g CO2 / g adsorbent in cycle 5, and further decreased to 0.177 g CO2 / g adsorbent in cycle 25, representing a performance degradation rate of 51% from cycle 5 to cycle 25. In contrast, the calcium-based carbon dioxide adsorbent prepared in Comparative Example 1 exhibited an adsorption capacity of 0.448 g CO2 / g adsorbent in cycle 1, 0.509 g CO2 / g adsorbent in cycle 5, and 0.504 g CO2 / g adsorbent in cycle 25, representing a performance degradation rate of 0.9% from cycle 5 to cycle 25. The calcium-based carbon dioxide adsorbent prepared by the method in Comparative Example 1 showed a 41% increase in adsorption capacity in the 5th cycle and a 184.7% increase in adsorption capacity in the 25th cycle compared to ordinary CaO. The stability of CO2 capture performance from the 5th to the 25th cycle was improved by 98.2%.

[0099] Comparative Example 2:

[0100] Measure 1 mol of calcium nitrate and 5 mol of glycine into a container, add a mixture containing 10 mol of deionized water and 10 mol of anhydrous ethanol to fully dissolve the calcium nitrate and glycine and mix them evenly to prepare a precursor solution.

[0101] The precursor solution was pressurized to 0.15 MPa using a liquid booster pump and then introduced into the liquid inlet of a pneumatic atomizing nozzle. The liquid outlet opening of the nozzle was adjusted to achieve a flow rate of 30 mL / min, forming a stable liquid column. An air compressor was then activated to generate compressed air at 0.1 MPa. This compressed air was then introduced into the gas inlet of the atomizing nozzle, and the gas outlet opening was adjusted to achieve a flow rate of 20 L / min. Under the shear force of the compressed air, the liquid column was atomized, forming a stable, extremely fine spray. The Sothel average particle size of the precursor solution spray was determined to be 16.2 μm using a laser particle size analyzer. The droplet group then entered a high-temperature vertical tube furnace at 900°C under the action of compressed air, where a vigorous combustion reaction occurred. The powdered product was collected at the end of the furnace, washed with anhydrous ethanol to remove impurities, filtered, and then vacuum dried to obtain the final product, a calcium-based carbon dioxide adsorbent.

[0102] Figure 15 These are TEM images of the calcium-based carbon dioxide adsorbent prepared using Comparative Example 2. Figure 11 Images a, b, and c in the image are of this sample at different magnifications, with scale bars of 0.5 μm, 200 nm, and 100 nm, respectively. It is evident that the method described in Comparative Example 2 cannot successfully prepare nanoscale particles with uniform particle size distribution and good sphericity; therefore, it is impossible to statistically analyze the average particle size.

[0103] Figure 16 The figure shows the cyclic CO2 capture performance curves of the spherical calcium nanoparticle-based carbon dioxide adsorbent prepared by Comparative Example 2. The performance curves of ordinary CaO under the same test conditions are also shown. Ordinary CaO, due to severe sintering during multiple carbonation-calcination cycles, experienced a decrease in its CO2 adsorption capacity from 0.663 g CO2 / g adsorbent in cycle 1 to 0.336 g CO2 / g adsorbent in cycle 6, and further decreased to 0.177 g CO2 / g adsorbent in cycle 25, representing a performance degradation rate of 47.3% from cycle 6 to cycle 25. In contrast, the calcium-based carbon dioxide adsorbent prepared by Comparative Example 2 exhibited an adsorption capacity of 0.458 g CO2 / g adsorbent in cycle 1, 0.551 g CO2 / g adsorbent in cycle 6, and 0.413 g CO2 / g adsorbent in cycle 25, representing a performance degradation rate of 25% from cycle 6 to cycle 25. The calcium-based carbon dioxide adsorbent prepared by the method described in Comparative Example 2 showed a 64% increase in adsorption capacity in the 6th cycle and a 133.3% increase in adsorption capacity in the 25th cycle compared to ordinary CaO. The CO2 capture performance stability from the 6th to the 25th cycle was improved by 47.1%.

[0104] The ordinary CaO involved in the above embodiments was formed by calcining analytical grade CaCO3 in a simultaneous thermal analyzer according to a pre-calcination procedure. Specifically, the sample was first pre-calcined in a N2 atmosphere at a rate of 100 ml / min: the temperature was increased from 20°C to 850°C at a rate of 30°C / min and held constant for 20 min to ensure complete decomposition of the CaCO3 in the sample. The analytical grade CaCO3 was purchased from Sinopharm Chemical Reagent Co., Ltd.

[0105] Ordinary CaO underwent severe sintering during multiple carbonation-calcination cycles under the same test conditions as in the above examples. This resulted in a decrease in its CO2 adsorption capacity from 0.663 g CO2 / g adsorbent in the first cycle to 0.439 g CO2 / g adsorbent in the third cycle, 0.361 g CO2 / g adsorbent in the fifth cycle, 0.336 g CO2 / g adsorbent in the sixth cycle, and finally to 0.177 g CO2 / g adsorbent in the twenty-fifth cycle. The performance degradation rate was 73.3% from the first to the fifth cycle, 59.7% from the third to the twenty-fifth cycle, 51% from the fifth to the twenty-fifth cycle, and 47.3% from the sixth to the twenty-fifth cycle.

[0106] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for synthesizing nanosphere-shaped calcium oxide carbon dioxide adsorbent, characterized in that, include: Calcium nitrate and organic fuel are dissolved in a solvent to prepare a precursor solution, wherein the solvent is deionized water or a mixture of deionized water and anhydrous ethanol. The precursor solution is pressurized and then passed through a pneumatic atomizing nozzle to form a precursor solution spray, which then enters a vertical tube furnace to undergo a combustion reaction. During this process, the precursor solution spray droplets explode to form multiple submicron-sized droplets. Each submicron-sized droplet then undergoes solute deposition, crystallization, and sintering agglomeration, ultimately producing nano-spherical calcium oxide carbon dioxide adsorbent. The flow rate of the precursor solution after pressurization is 5 ~ 50 mL / min; the flow rate of compressed air in the pneumatic atomizing nozzle is 10 ~ 50 L / min.

2. The method for synthesizing nano-spherical calcium oxide carbon dioxide adsorbent according to claim 1, characterized in that, The size of the precursor solution spray is 0.1 ~ 15 μm.

3. The method for synthesizing nano-spherical calcium oxide carbon dioxide adsorbent according to claim 1, characterized in that, The molar ratio of the organic fuel to the calcium nitrate is (0.2 ~ 3):

1.

4. The method for synthesizing nano-spherical calcium oxide carbon dioxide adsorbent according to claim 3, characterized in that, The molar ratio of the organic fuel to the calcium nitrate is (0.5 ~ 1.5):

1.

5. The method for synthesizing nano-spherical calcium oxide carbon dioxide adsorbent according to claim 1, characterized in that, The organic fuel includes at least one of the following: organic acids or sugars; or a combination of at least one organic acid and at least one sugar. The organic acids include acetic acid, propionic acid, lactic acid, citric acid, malic acid, tartaric acid, or glycine; the sugars include glucose or fructose.

6. The method for synthesizing nano-spherical calcium oxide carbon dioxide adsorbent according to claim 1, characterized in that, The precursor solution also contains a metal nitrate that can decompose to form a high-melting-point metal oxide, wherein the high-melting-point metal oxide has a melting point greater than 1600 °C. The molar ratio of the metal nitrate that can decompose to form a high-melting-point metal oxide to the calcium nitrate is (0 ~ 0.4):

1.

7. The method for synthesizing nano-spherical calcium oxide carbon dioxide adsorbent according to claim 6, characterized in that, The molar ratio of the metal nitrate that can decompose to form a high-melting-point metal oxide to the calcium nitrate is (0.1~0.2):

1.

8. The method for synthesizing nano-spherical calcium oxide carbon dioxide adsorbent according to claim 1, characterized in that, The molar ratio of anhydrous ethanol to deionized water is (0.1 ~ 3): 1; The molar ratio of the solvent to the calcium nitrate is (10 ~ 40):

1.

9. The method for synthesizing nano-spherical calcium oxide carbon dioxide adsorbent according to claim 1, characterized in that, The temperature of the vertical tube furnace is 500 ~ 1000℃, and combustion occurs inside the vertical tube furnace.

10. The method for synthesizing nano-spherical calcium oxide carbon dioxide adsorbent according to claim 9, characterized in that, The temperature of the vertical tube furnace is 600 ~ 900℃.

11. The method for synthesizing nano-spherical calcium oxide carbon dioxide adsorbent according to claim 1, characterized in that, The vertical tube furnace has a tube length of 1000-2000 mm and an inner diameter of 100-400 mm.

12. The nanosphere calcium oxide carbon dioxide adsorbent prepared by the method according to any one of claims 1-11.

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