CN117463283B - A hollow microsphere-structured calcium oxide-based CO2 adsorbent and its preparation method - Google Patents

Abstract

This invention provides a method for preparing a hollow microsphere-structured calcium oxide-based _CO2 adsorbent. Compared with existing technologies, this invention uses a one-pot method to prepare the adsorbent, forming a hollow microsphere morphology. This morphology facilitates _CO2 diffusion, thus significantly improving the adsorption capacity and adsorption rate. Furthermore, the hollow volume inside the microspheres can adapt to volume changes during the reaction process, exhibiting a certain degree of resistance to sintering. Simultaneously, cerium doping reduces the particle size of calcium oxide, and the well-dispersed cerium oxide also acts as a barrier, effectively preventing the growth and sintering of calcium oxide microcrystals. This results in excellent stability of the adsorbent. Cerium doping also increases the carbonization rate of the adsorbent, thereby achieving a high adsorption capacity in a short time.

Description

Calcium oxide-based CO 2 adsorbent with hollow microsphere structure and preparation method thereof

Technical Field

The invention belongs to the technical field of solid adsorbents, and particularly relates to a calcium oxide-based CO ₂ adsorbent with a hollow microsphere structure and a preparation method thereof.

Background

Carbon dioxide (CO ₂) is one of the most dominant greenhouse gases, and with the rapid development of global economy, the consumption of fossil energy is great, and the content of CO ₂ in the atmosphere is rapidly increased, so that global environmental ecological problems such as global warming, ocean acidification, glacier melting and extreme weather are increasingly serious. Therefore, reduction of CO ₂ is urgent.

Compared with the traditional solvent absorption process, the solid adsorbent has the advantages of wider operating temperature range, capability of changing from room temperature to 700 ℃, low loss in the circulation process, little environmental pollution, relatively simple process, low running cost and the like. The solid adsorbent can be classified into a low-temperature adsorbent, a medium-temperature adsorbent and a high-temperature adsorbent from the working temperature. Low temperature adsorbents (< 200 ℃) are mainly molecular sieves, carbon based materials, MOFs, etc. The medium-temperature adsorbent (200-400 ℃) mainly comprises Layered Double Hydroxide (LDH), magnesium oxide (MgO) and the like. The high-temperature adsorbent (> 400 ℃) mainly comprises CaO, lithium zirconate and the like. From the viewpoint of effective utilization of energy, the high-temperature CO ₂ trapping technology is more advantageous because the high-temperature gas does not need to be subjected to a cooling process, and the high-temperature solid adsorbent is used for directly absorbing CO ₂, so that a large amount of energy loss can be avoided, resources are saved, and cost is reduced. Therefore, the development of the high-temperature adsorbent has wide prospect. Lithium salts such as lithium zirconate can be directly used for high temperature adsorption, but are unfavorable for large-scale popularization due to high manufacturing cost. Whereas CaO is widely present in nature in the form of calcium carbonate and therefore represents a very potential commercial basis.

With the reversible reaction of CaO+CO ₂-→CaCO₃, caO is usually adsorbed to CO ₂ at a high temperature above 600 ℃ to form CaCO ₃, and is calcined and desorbed to CO ₂ at a higher temperature, such as 850 ℃, so that CaO is regenerated. Through investigation, researches on CaO-based adsorbents mainly focus on two aspects, namely, the initial adsorption capacity is further improved, and various methods are adopted to slow down CaO sintering and improve the stability and adsorption efficiency.

Muller et al prepared a Mg-doped CaO multilayer microporous structure by template-assisted hydrothermal synthesis using xylose as a template agent and urea as a precipitant. Wherein MgO is uniformly mixed with CaO at the nano level and serves as an inert structural stabilizer which can delay sintering. The introduction of the carbonaceous template in the synthesis process is favorable for forming a multi-shell structure with rich pores and regular structure after high-temperature roasting and removal, which is the key for efficiently absorbing CO ₂. Three different components of adsorbents Ca90Mg10, ca85Mg15 and Ca80Mg20 were prepared by optimizing Ca: mg. It was found that MgO content as low as 15mol% (i.e. 11 wt.%) in Ca85Mg15 was sufficient to obtain a high level of cycle stability, and that after 30 cycles of CO ₂ capture and regeneration, the adsorption capacity could be kept at 83% of the initial adsorption capacity, about 500% higher than limestone derived CaO. However, since Mg is introduced to occupy a certain adsorption site, the adsorption amount is lost although the circulation stability of the adsorbent is improved.

Disclosure of Invention

In view of the above, the technical problem to be solved by the present invention is to provide a hollow microsphere-structured calcium oxide-based CO ₂ adsorbent with higher carbon dioxide adsorption capacity, adsorption rate and higher sintering resistance, and a preparation method thereof.

The invention provides a preparation method of a hollow microsphere structure calcium oxide-based CO ₂ adsorbent, which comprises the following steps:

s1) mixing glucose, soluble calcium salt and soluble cerium salt in water to obtain a mixed solution;

s2) adding urea aqueous solution into the mixed solution, and heating for reaction to obtain a solid substance;

And S3) calcining the solid substance to obtain the calcium oxide-based CO ₂ adsorbent with the hollow microsphere structure.

Preferably, the molar ratio of cerium element in the soluble cerium salt to calcium element in the soluble calcium salt is 0.005-0.1:1.

Preferably, the molar ratio of urea to calcium element in the soluble calcium salt is less than 0.55.

Preferably, the molar ratio of glucose to calcium element in the soluble calcium salt is (2-2.1): 1.

Preferably, the concentration of the urea solution is 0.15-2 g/mL, and the volume ratio of the urea aqueous solution to the mixed solution is 1 (4.5-5.5).

Preferably, the temperature of the heating reaction in the step S2) is 165-175 ℃, and the time of the heating reaction is 15-30 hours.

Preferably, the calcination temperature in the step S3) is 750-850 ℃, the calcination time is 0.5-2 h, and the calcination temperature rising rate is 3-6 ℃ per minute.

The invention also provides the calcium oxide-based CO ₂ adsorbent with the hollow microsphere structure prepared by the preparation method.

The invention also provides application of the hollow microsphere structure calcium oxide-based CO ₂ adsorbent prepared by the preparation method in CO ₂ adsorption.

The invention provides a preparation method of a calcium oxide-based CO ₂ adsorbent with a hollow microsphere structure, which comprises the following steps of S1) mixing glucose, soluble calcium salt and soluble cerium salt in water to obtain a mixed solution, S2) adding urea aqueous solution into the mixed solution, heating and reacting to obtain a solid substance, and S3) calcining the solid substance to obtain the calcium oxide-based CO ₂ adsorbent with the hollow microsphere structure. Compared with the prior art, the invention adopts a one-pot method to prepare the adsorbent, glucose can form carbon spheres in the heating process, certain pores are formed in the carbon spheres, certain hydrophilic groups are arranged on the surfaces, a part of calcium ions and cerium ions can enter the carbon spheres, and a part of calcium ions and cerium ions can be adhered to the surfaces of the carbon spheres through the hydrophilic groups, so that under the action of urea, the whole system is in a proper alkaline environment, calcium ions and cerium ions are uniformly distributed on the surfaces of the carbon spheres, in addition, the carbonate formed by hydrolysis of urea can enable a part of calcium ions and cerium ions to be precipitated on the surfaces of the carbon spheres in the form of carbonate, when the template agent is removed by high-temperature roasting, metal ions in the carbon spheres and on the surfaces can better interact to form hollow microsphere morphology, and the morphology is favorable for diffusion of CO ₂, so that the adsorption capacity and adsorption rate are remarkably improved, in addition, the hollow volume in the hollow microspheres can adapt to the change of the volume in the reaction process, the doping of cerium elements can reduce the particle size of calcium oxide, the dispersed cerium oxide can also play a role in blocking, and the calcium oxide can effectively prevent the growth of cerium oxide and the cerium oxide from growing in a short time, so that the adsorbent can obtain the excellent adsorption capacity of the adsorbent can be better in the adsorption capacity.

Experimental results show that the Ce doped in the preparation method provided by the invention can reduce the grain size of CaO, and CeO ₂ with good dispersion can effectively prevent the growth and sintering of CaO microcrystals, so that the adsorbent shows excellent stability, the carbonization rate of the adsorbent is improved, and higher adsorption capacity is obtained in a short time. The obtained Ce-CaO solid adsorbent has the adsorption capacity to CO ₂ after 15 cycles, which is almost the same as that of the first cycle.

Drawings

FIG. 1 is an SEM image of a Ce-CaO solid adsorbent obtained in example 4 of the present invention;

FIG. 2 is an EDS diagram of a Ce-CaO solid adsorbent obtained in example 4 of the present invention;

FIG. 3 is a graph showing the adsorption performance test of CO ₂ of the Ce-CaO solid adsorbent obtained in example 4 of the present invention;

FIG. 4 is a graph showing the adsorption performance test of the solid Ce-CaO adsorbent CO ₂ with different Ce doping amounts obtained in examples 1 to 4 of the present invention;

FIG. 5 is a graph showing the adsorption performance test of CO ₂ of the Ce-CaO solid adsorbent prepared in comparative example 1, according to example 4 of the present invention.

Detailed Description

The technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention, and it is apparent that the described embodiments are only some embodiments of the present invention, not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.

In the description and in the claims, the terms "comprising," including, "and" containing "are to be construed as open-ended, meaning" including, but not limited to, unless the context requires otherwise.

Reference in the specification to "an embodiment," "one embodiment," "another embodiment," or "certain embodiments," etc., means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, it is not necessary for an "embodiment," "one embodiment," "another embodiment," or "certain embodiments" to refer to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. The various features disclosed in the specification may be replaced by alternative features serving the same, equivalent or similar purpose. Thus, unless expressly stated otherwise, the disclosed features are merely general examples of equivalent or similar features.

The invention will be further illustrated with reference to specific examples. It is to be understood that these examples are illustrative of the present invention and are not intended to limit the scope of the present invention. The experimental procedures, which do not address the specific conditions in the examples below, are generally carried out under conventional conditions or under conditions recommended by the manufacturer. All percentages, ratios, proportions, or parts are by weight unless otherwise indicated.

The units in weight volume percent are well known to those skilled in the art and refer, for example, to the weight of solute in 100 milliliters of solution.

In the present invention, the concentration unit "M" of the solution represents mol/L.

The "one-pot method" means that the reactants are continuously reacted in one reactor in a multi-step manner to directly obtain the target substance without separation of intermediates.

The invention provides a preparation method of a calcium oxide-based CO ₂ adsorbent with a hollow microsphere structure, which comprises the following steps of S1) mixing glucose, soluble calcium salt and soluble cerium salt in water to obtain a mixed solution, S2) adding urea aqueous solution into the mixed solution, heating and reacting to obtain a solid substance, and S3) calcining the solid substance to obtain the calcium oxide-based CO ₂ adsorbent with the hollow microsphere structure.

The source of all the raw materials is not particularly limited, and the raw materials are commercially available.

The glucose, the soluble calcium salt and the soluble cerium salt are mixed in water to obtain a mixed solution, the molar ratio of the glucose to the calcium element in the soluble calcium salt is preferably (2-2.1): 1, more preferably 2:1, the soluble calcium salt is a soluble calcium salt well known to a person skilled in the art and is not particularly limited, the soluble cerium salt is a soluble cerium salt well known to a person skilled in the art and is not particularly limited, the soluble cerium salt is preferably not limited to cerium nitrate, the molar ratio of the cerium element in the soluble cerium salt to the calcium element in the soluble calcium salt is preferably 0.005-0.1:1, the molar ratio of the cerium element in the soluble cerium salt to the calcium element in the soluble calcium salt is particularly 0.1:1, 0.05:1, 0.02:1 or 0.005:1, the doping amount of the element is controlled to ensure calcium oxide-based CO ₂, the mixing time is preferably 5 m/2, the mixing time is preferably 10-2.5 m/5 m/2, and the mixing time is preferably 10.5 m/5 m/2 m 2.5m 2, and the mixing time is preferably 10-2.5 m 2.

The method comprises the steps of adding urea aqueous solution into mixed solution, heating and reacting to obtain solid matters, preferably dropwise adding the urea aqueous solution into the mixed solution, wherein the concentration of the urea aqueous solution is preferably 0.15-2 g/mL, more preferably 0.15-1 g/mL, still more preferably 0.15-0.5 g/mL, still more preferably 0.15-0.3 g/mL, most preferably 0.18-0.2 g/mL, the volume ratio of the urea aqueous solution to the mixed solution is preferably 1 (4.5-5.5), more preferably 1:5, the molar ratio of the urea to calcium element in the soluble calcium salt is preferably less than 0.55, more preferably 0.4-0.54, still more preferably 0.45-0.54, still preferably 0.5-0.53, most preferably 0.52-0.53, and adding a proper amount of urea can keep proper alkalinity in the mixed solution, so that a part of CaCO ₃ can be uniformly precipitated on a template and form, and the required carbonate ions can be uniformly distributed on the surface of the carbon and the surface of the carbon carbonate balls can be formed. Under the condition of NO urea, ca (NO ₃)₂) is simply added into a glucose solution, and then the product is calcined to generate a cyclic CaO structure instead of a required form, the urea aqueous solution is preferably stirred after being added into the mixed solution and then subjected to a heating reaction, wherein the stirring time is preferably 1-10 min, more preferably 2-8 min, still more preferably 4-6 min, most preferably 5min, the heating reaction temperature is preferably 165-175 ℃, more preferably 170 ℃, the heating reaction time is preferably 15-30 h, more preferably 20-28 h, still more preferably 22-26 h, most preferably 24h, and the solid matter is obtained after the heating reaction and filtration.

According to the invention, ce is introduced while CaCO ₃ is precipitated on the template agent, and the amount of CaCO ₃ precipitated on the template agent is enough to form carbon spheres under the alkaline condition of proper urea hydrolysis, so that the hollow microsphere morphology of the Ce-CaO adsorbent can be reserved after subsequent processes such as roasting. And Ce can be better dispersed on the surface or in pores of the carbon sphere. This process not only involves the precipitation of CaCO ₃ onto the formed carbon spheres, but also involves the adsorption of some Ca onto the carbon spheres by electrostatic attraction, which, when burned, forms a hollow microsphere morphology with the precipitated CaCO ₃. Compared with the adsorbent obtained by doping Ce into CaO hollow microspheres by the impregnation method, the dispersion of Ce is relatively uneven in the adsorbent obtained by the impregnation method, and the influence of Ce on the lattice structure of Ca element is larger during roasting, so that the original hollow microsphere appearance cannot be well reserved, and further, the carbonization rate, adsorption capacity, service life and the like of the adsorbent are adversely affected.

The solid substance is calcined to obtain the calcium oxide-based CO ₂ adsorbent with a hollow microsphere structure, the solid substance is preferably washed by water and ethanol and then is dried and then calcined, the drying temperature is preferably 60-100 ℃, more preferably 70-90 ℃ and still more preferably 80 ℃, the drying time is preferably 8-20 h, more preferably 10-15 h and still more preferably 12h, the calcining temperature is preferably 750-850 ℃, more preferably 780-820 ℃ and still more preferably 800 ℃, the template agent can be well removed within the calcining temperature range, so that the adsorbent can obtain a crystal structure and a pore size which are beneficial to CO ₂ adsorption, the calcining time is preferably 0.5-2 h, more preferably 0.8-1.5 h and still more preferably 1h, and the temperature rising rate from room temperature to the calcining temperature is controlled within a certain range, and the temperature rising rate is controlled to influence the microsphere structure and morphology in the calcining process. The faster heating rate can cause uneven surface appearance of the microspheres, while the slower heating rate can promote uniform growth inside the microspheres, which is unfavorable for the formation of hollow microspheres. In the invention, the temperature rising rate of calcination is preferably 3-6 ℃ per minute, more preferably 4-6 ℃ per minute, and still more preferably 5 ℃. The Ce-CaO hollow porous microspheres are obtained by controlling the temperature rising rate and the calcination temperature in the calcination process, and the pores are uniformly distributed, so that the adsorption quantity of CO ₂ is improved. If the pore distribution inside the microsphere is not uniform, some sites may have too small pores to sufficiently adsorb CO ₂ molecules, resulting in a decrease in the amount of adsorbed CO ₂.

According to the invention, an adsorbent is prepared by adopting a one-pot method, glucose can form carbon spheres in the heating process, certain pores exist in the carbon spheres, certain hydrophilic groups are arranged on the surfaces, a part of calcium ions and cerium ions can enter the carbon spheres, a part of calcium ions and cerium ions can be attached to the surfaces of the carbon spheres through the hydrophilic groups, and further under the action of urea, the whole system is in a proper alkaline environment, so that the calcium ions and cerium ions are uniformly distributed on the surfaces of the carbon spheres, in addition, the carbonate formed by hydrolysis of urea can enable a part of calcium ions and cerium ions to be deposited on the surfaces of the carbon spheres in the form of carbonate, when the template agent is removed by high-temperature roasting, metal ions in the carbon spheres and on the surfaces can better interact to form hollow microsphere morphology, the morphology is favorable for the diffusion of CO ₂, so that the adsorption capacity and adsorption rate are remarkably improved, in addition, the hollow volume in the hollow microsphere can adapt to the change of volume in the reaction process, the doping of cerium element can reduce the particle size of calcium oxide, the well-dispersed cerium oxide can play a blocking role, the growth of calcium oxide can be effectively prevented, the growth of cerium oxide and the cerium oxide can be well-doped in the adsorption rate of the adsorbent, and the adsorbent can be well-doped in the adsorption rate and has high adsorption capacity and high adsorption capacity.

The invention also provides the calcium oxide-based CO ₂ adsorbent with the hollow microsphere structure prepared by the preparation method.

The invention also provides application of the hollow microsphere structure calcium oxide-based CO ₂ adsorbent prepared by the preparation method in CO ₂ adsorption.

In order to further illustrate the present invention, the following examples are provided to describe the calcium oxide-based CO ₂ adsorbent having a hollow microsphere structure and the preparation method thereof in detail.

The reagents used in the examples below are all commercially available.

Example 1

6.10G of glucose, 4.0g of calcium nitrate tetrahydrate and 0.7375g of cerium nitrate hexahydrate were weighed into a beaker, 15mL of deionized water was added thereto, and stirred for 15 minutes to obtain a first solution. 0.54g of urea was weighed and dissolved in 3mL of deionized water to obtain a second solution. The second solution was added dropwise to the first solution, and stirred for 5 minutes to obtain a third solution. The third solution was placed in a reaction kettle and reacted at 170 ℃ for 24 hours, followed by suction filtration to obtain a solid substance.

The solid material was washed with 2000mL deionized water and then 500mL ethanol, and the filtered solid sample was dried in an 80 ℃ oven for 12 hours. The dried sample was taken out, ground into powder, and calcined. Calcining at 800 ℃ for 1 hour at a temperature rising rate of 5 ℃ per minute to obtain the Ce-stabilized CaO-based solid adsorbent, wherein the sample is named Ca3M-10Ce.

Example 2

6.10G of glucose, 4.0g of calcium nitrate tetrahydrate and 0.3673g of cerium nitrate hexahydrate were weighed into a beaker, 15mL of deionized water was added thereto, and stirred for 15 minutes to obtain a first solution. 0.54g of urea was weighed and dissolved in 3mL of deionized water to obtain a second solution. The second solution was added dropwise to the first solution, and stirred for 5 minutes to obtain a third solution. The third solution was placed in a reaction kettle and reacted at 170 ℃ for 24 hours, followed by suction filtration to obtain a solid substance.

The solid material was washed with 2000mL deionized water and then 500mL ethanol, and the filtered solid sample was dried in an 80 ℃ oven for 12 hours. The dried sample was taken out, ground into powder, and calcined. Calcining at 800 ℃ for 1 hour at a temperature rising rate of 5 ℃ per minute to obtain the Ce-stabilized CaO-based solid adsorbent, wherein the sample is named Ca3M-5Ce.

Example 3

6.10G of glucose, 4.0g of calcium nitrate tetrahydrate and 0.1471g of cerium nitrate hexahydrate were weighed into a beaker, 15mL of deionized water was added thereto, and stirred for 15 minutes to obtain a first solution. 0.54g of urea was weighed and dissolved in 3mL of deionized water to obtain a second solution. The second solution was added dropwise to the first solution, and stirred for 5 minutes to obtain a third solution. The third solution was placed in a reaction kettle and reacted at 170 ℃ for 24 hours, followed by suction filtration to obtain a solid substance.

The solid material was washed with 2000mL deionized water and then 500mL ethanol, and the filtered solid sample was dried in an 80 ℃ oven for 12 hours. The dried sample was taken out, ground into powder, and calcined. Calcining at 800 ℃ for 1 hour at a temperature rising rate of 5 ℃ per minute to obtain the Ce-stabilized CaO-based solid adsorbent, wherein the sample is named Ca3M-2Ce.

Example 4

6.10G of glucose, 4.0g of calcium nitrate tetrahydrate and 0.03678g of cerium nitrate hexahydrate were weighed into a beaker, 15mL of deionized water was added thereto, and stirred for 15 minutes to obtain a first solution. 0.54g of urea was weighed and dissolved in 3mL of deionized water to obtain a second solution. The second solution was added dropwise to the first solution, and stirred for 5 minutes to obtain a third solution. The third solution was placed in a reaction kettle and reacted at 170 ℃ for 24 hours, followed by suction filtration to obtain a solid substance.

The solid material was washed with 2000mL deionized water and then 500mL ethanol, and the filtered solid sample was dried in an 80 ℃ oven for 12 hours. The dried sample was taken out, ground into powder, and calcined. Calcining at 800 ℃ for 1 hour at a temperature rising rate of 5 ℃ per minute to obtain the Ce-stabilized CaO-based solid adsorbent, wherein the sample is named Ca3M-0.5Ce.

Comparative example 1

The comparative example was prepared using a two-step process:

Firstly, preparing a Ce-free calcium oxide-based adsorbent, namely weighing 6.10g of glucose and 4.0g of calcium nitrate tetrahydrate in a beaker, adding 15mL of deionized water into the mixture, and stirring the mixture for 15 minutes to obtain a first solution. 0.54g of urea was weighed and dissolved in 3mL of deionized water to obtain a second solution. The second solution was added dropwise to the first solution, and stirred for 5 minutes to obtain a third solution. The third solution was placed in a reaction kettle and reacted at 170 ℃ for 24 hours, followed by suction filtration to obtain a solid substance.

The solid material was washed with 2000mL deionized water and then 500mL ethanol, and the filtered solid sample was placed in an 80 ℃ oven and dried for at least 12 hours. The dried sample was taken out, ground into powder, and calcined. Calcination process roasting at 800 deg.c for 1 hr at 5 deg.c/min to obtain CaO-based solid adsorbent, which is named Ca3M.

Next, ce was introduced by dipping, 0.5g of Ca3M was weighed, 0.00638g of cerium nitrate hexahydrate was added, 10g of deionized water was added, and then stirred at room temperature for 12 hours. Then the water was evaporated to dryness at 130 ℃ with stirring at 90 ℃ for 12h. Drying, and placing in a programmed temperature muffle furnace, calcining at 500 ℃ for 2 hours, wherein the temperature rising rate is 2 ℃ per minute. The resulting sample was designated Ca3M-5Ce-imp.

The solid Ce-CaO adsorbent prepared in example 4 was analyzed by using a JSM-7900F scanning electron microscope (see FIG. 1), the morphology of the adsorbent was tested under the test condition of an acceleration voltage of 2kV, and the elements on the surface of the sample were analyzed by using EDS. The preparation before testing is that the conductive adhesive tape is adhered on the sample holder, then the sample powder is evenly placed on the conductive adhesive tape, then the non-adhered sample powder is blown away by compressed air, then heavy metal plating operation is carried out to ensure conductivity, and finally scanning test is carried out. As a result, it was found that the adsorbent having Ce incorporation of 0.5% maintained the morphology of the sphere, as shown in fig. 2. From the results of the X-ray spectroscopy (EDS), it is known that Ce element was successfully introduced and Ce was uniformly distributed on the microsphere surface as shown in fig. 2 below.

CO ₂ adsorption performance test on the Ce-CaO solid adsorbent prepared in example 4 CO ₂ adsorption performance test was performed on the adsorbent prepared in example 4 using a thermogravimetric analyzer model TGA/DSC 3+ from Metrele-Toli Multi instruments Co. For each test, less than 10mg of adsorbent was placed on an alumina crucible. At the beginning of each adsorption process, the sample was held at 100vol% n ₂ for 30 minutes at 850 ℃. The adsorption process was maintained at 650 ℃ for 30 minutes under an atmosphere of 15vol% co ₂/85vol％N₂. The desorption process was carried out at 850 ℃,85vol% n ₂ for 10 minutes. The temperature rise and the temperature drop rates are both kept at 20 ℃ per minute. As a result, it was found (refer to FIG. 3) that the adsorbent having Ce incorporated amount of 0.5% had the optimum adsorption amount and the best cycle stability. The adsorption capacity of CO ₂ is still maintained at 8.56 mmol.g ^-1 after 15 cycles, which is comparable to that of 8.92 mmol.g ^-1 of the first cycle.

In addition, the solid adsorbents of Ce-CaO of examples 1 to 4 with different Ce doping amounts were subjected to CO ₂ adsorption performance test, the method is as described above, and the results are shown in FIG. 4. As can be seen from FIG. 4, the Ce-CaO solid adsorbent prepared in example 4 has a very high adsorption capacity.

The ce—cao solid adsorbents prepared in example 4 and comparative example 1 were subjected to CO ₂ adsorption performance test. The specific experimental method is as above. As shown in FIG. 5, the adsorption amount of the Ce-CaO solid adsorbent prepared by the impregnation method is significantly lower than that of the Ce-CaO solid adsorbent prepared by the one-pot method. On the one hand, in the adsorbent prepared by the impregnation method, cerium has poor dispersibility and occupies adsorption sites, and on the other hand, the impregnation method damages the original structure of CaO.

Claims (9)

1. A method for preparing a hollow microsphere-structured calcium oxide-based _CO2 adsorbent, characterized by comprising the following steps: S1) Glucose, soluble calcium salt and soluble cerium salt are mixed in water to obtain a mixture; S2) Add urea aqueous solution to the mixture, heat and react to obtain a solid substance; S3) The solid material is calcined to obtain a hollow microsphere structure calcium oxide-based _CO2 adsorbent; the calcination heating rate is 3~6℃/min. 2. The preparation method according to claim 1, wherein the molar ratio of cerium in the soluble cerium salt to calcium in the soluble calcium salt is 0.005~0.1:1. 3. The preparation method according to claim 1, wherein the molar ratio of urea to calcium in the soluble calcium salt is less than 0.55. 4. The preparation method according to claim 1, wherein the molar ratio of glucose to calcium in the soluble calcium salt is (2~2.1):1. 5. The preparation method according to claim 1, wherein the concentration of the urea solution is 0.15~2 g/mL; and the volume ratio of the urea aqueous solution to the mixed solution is 1:(4.5~5.5). 6. The preparation method according to claim 1, wherein the heating reaction temperature in step S2) is 165℃~175℃; and the heating reaction time is 15~30 h. 7. The preparation method according to claim 1, wherein the calcination temperature in step S3) is 750℃~850℃; and the calcination time is 0.5~2 h. 8. The hollow microsphere-structured calcium oxide-based _CO2 adsorbent prepared by any one of claims 1 to 7. 9. The application of the hollow microsphere-structured calcium oxide-based _CO2 adsorbent prepared by any one of claims 1 to 7 in the adsorption of _CO2 .