A hollow microsphere structured calcium oxide-based co2 adsorbent and a method for preparing the same

Abstract

The application provides a preparation method of a hollow microsphere structure calcium oxide-based CO2 adsorbent. Compared with the prior art, the adsorbent is prepared by a one-pot method to form a hollow microsphere morphology, the morphology is beneficial to the diffusion of CO2, and thus the adsorption capacity and the adsorption rate are significantly improved; in addition, the hollow volume inside the hollow microsphere can adapt to the volume change in the reaction process, and has a certain anti-sintering capacity; meanwhile, the doping of cerium elements can reduce the particle size of calcium oxide, and the well-dispersed cerium oxide can also play a blocking role, effectively preventing the growth and sintering of calcium oxide microcrystals, so that the adsorbent exhibits excellent stability; the doping of cerium oxide also improves the carbonization rate of the adsorbent, and thus a higher adsorption capacity can be obtained in a short time.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of solid adsorbents, and particularly relates to a hollow microsphere structure calcium oxide-based CO2 adsorbent and a preparation method thereof. BACKGROUND

[0002] Carbon dioxide (CO2) is one of the most important greenhouse gases. With the rapid development of the global economy and the large consumption of fossil energy, the content of CO2 in the atmosphere has risen sharply, leading to global warming, ocean acidification, glacier melting, and extreme weather, and other global environmental and ecological problems are becoming increasingly serious. Therefore, CO2 emission reduction is imminent.

[0003] Compared with the traditional solvent absorption process, the solid adsorbent has the advantages of a wide operating temperature range, low loss in the cycle process, small environmental pollution, a relatively simple process, and low operation cost. The solid adsorbent can be divided into three categories according to the working temperature, i.e., a low-temperature adsorbent (<200℃), a medium-temperature adsorbent (200℃-400℃), and a high-temperature adsorbent (>400℃). The low-temperature adsorbent mainly includes molecular sieves, carbon-based materials, and MOFs. The medium-temperature adsorbent mainly includes layered double hydroxides (LDH) and magnesium oxide (MgO). The high-temperature adsorbent mainly includes CaO and lithium zirconate. From the perspective of effective utilization of energy, the high-temperature CO2 capture technology has more advantages, because the high-temperature gas does not need to be cooled, and the CO2 is directly absorbed by using the high-temperature solid adsorbent, so that a large amount of energy loss can be avoided, resources can be saved, and the cost can be reduced. Therefore, the development of the high-temperature adsorbent has broad prospects. Lithium salts such as lithium zirconate can be directly used for high-temperature adsorption, but due to the high manufacturing cost, it is not conducive to large-scale promotion. CaO exists in the form of calcium carbonate in nature, and therefore has great potential for commercial use.

[0004] CaO+CO2-→CaCO3 reversible reaction can be used, CaO usually adsorbs CO2 to generate CaCO3 at a high temperature of 600℃ or higher, and CaO can be regenerated by calcining at a higher temperature such as 850℃ to desorb CO2. Through investigation, it is found that the researches on the CaO-based adsorbent mainly focus on two aspects, one is to further improve the initial adsorption capacity, and the other is to take various methods to slow down the sintering of CaO, and improve the stability and adsorption efficiency.

[0005] Muller et al. synthesized Mg-doped CaO with hierarchical micro- and mesoporous structure by template-assisted hydrothermal synthesis using xylose as a templating agent and urea as a precipitating agent. The MgO was uniformly mixed with CaO at the nanoscale and acted as an inert structure stabilizer that could delay sintering. The introduction of carbonaceous templates during synthesis was beneficial to the formation of a multi-shell structure with abundant pores and regular structure after removal by high-temperature calcination, which was a key to efficient CO2 absorption. Three adsorbents with different compositions, Ca90Mg10, Ca85Mg15 and Ca80Mg20, were prepared by optimizing the Ca:Mg ratio. It was found that a MgO content as low as 15 mol% (i.e. 11 wt.%) in Ca85Mg15 was sufficient to achieve a high level of cycle stability, and the adsorption capacity could remain 83% of the initial adsorption capacity after 30 cycles of CO2 capture and regeneration, which was about 500% higher than that of limestone-derived CaO. However, due to the introduction of Mg, which occupied a certain number of adsorption sites, although the cycle stability of the adsorbent was improved, the adsorption capacity was lost. SUMMARY

[0006] Therefore, the present application aims to provide a hollow microsphere structure calcium oxide-based CO2 adsorbent with high CO2 adsorption capacity, adsorption rate and high sintering resistance, and a preparation method thereof.

[0007] The present application provides a preparation method of a hollow microsphere structure calcium oxide-based CO2 adsorbent, comprising the following steps:

[0008] S1) mixing glucose, a soluble calcium salt and a soluble cerium salt in water to obtain a mixed solution;

[0009] S2) adding an aqueous urea solution to the mixed solution, and obtaining a solid substance after heating and reaction;

[0010] S3) calcining the solid substance to obtain a hollow microsphere structure calcium oxide-based CO2 adsorbent.

[0011] Preferably, the molar ratio of cerium in the soluble cerium salt to calcium in the soluble calcium salt is 0.005-0.1:1.

[0012] Preferably, the molar ratio of urea to calcium in the soluble calcium salt is less than 0.55.

[0013] Preferably, the molar ratio of glucose to calcium in the soluble calcium salt is (2-2.1):1.

[0014] Preferably, the concentration of the urea solution is 0.15-2 g / mL; and the volume ratio of the aqueous urea solution to the mixed solution is 1:(4.5-5.5).

[0015] Preferably, the heating reaction in step S2) is performed at a temperature of 165-175 DEG C for 15-30 hours.

[0016] Preferably, the calcination in step S3) is performed at a temperature of 750-850 DEG C for 0.5-2 hours at a heating rate of 3-6 DEG C / min.

[0017] The application also provides a hollow microspherical structure calcium oxide-based CO2 adsorbent prepared by the above preparation method.

[0018] The application also provides a use of the hollow microspherical structure calcium oxide-based CO2 adsorbent prepared by the above preparation method in adsorbing CO2.

[0019] The application provides a preparation method of a hollow microspherical structure calcium oxide-based CO2 adsorbent, comprising the following steps: S1) mixing glucose, a soluble calcium salt and a soluble cerium salt in water to obtain a mixed solution; S2) adding an aqueous urea solution to the mixed solution, and obtaining a solid substance after heating reaction; and S3) calcining the solid substance to obtain a hollow microspherical structure calcium oxide-based CO2 adsorbent. Compared with the prior art, the adsorbent is prepared by a "one-pot method" in the application, and the glucose will form carbon spheres in the heating process. The carbon spheres have certain pores inside and certain hydrophilic groups on the surface. A part of calcium ions and cerium ions will enter the inside of the carbon spheres, and a part will be attached to the surface of the carbon spheres through the hydrophilic groups. The whole system is in a proper alkaline environment under the action of urea, which is beneficial to the uniform distribution of calcium ions and cerium ions on the surface of the carbon spheres. In addition, the calcium carbonate formed by the hydrolysis of urea can also make a part of calcium ions and cerium ions precipitate in the form of carbonate on the surface of the carbon spheres. When the template agent is removed at high temperature, the metal ions inside and on the surface of the carbon spheres can better interact to form a hollow microspherical morphology. The morphology is beneficial to the diffusion of CO2, thereby significantly improving the adsorption capacity and adsorption rate. In addition, the hollow volume inside the hollow microspheres can adapt to the volume change in the reaction process, and has a certain anti-sintering ability. At the same time, the doping of cerium elements can reduce the particle size of calcium oxide, and the well-dispersed cerium oxide can also play a blocking role, effectively preventing the growth and sintering of calcium oxide microcrystals, so that the adsorbent exhibits excellent stability. The doping of cerium oxide also improves the carbonization rate of the adsorbent, thereby obtaining a higher adsorption capacity in a short time.

[0020] The experimental results show that the Ce incorporated in the preparation method provided by the application can reduce the particle size of CaO, the well-dispersed CeO2 can effectively prevent the growth and sintering of CaO microcrystals, so that the adsorbent exhibits excellent stability, improves the carbonization rate of the adsorbent, and obtains a higher adsorption capacity in a short time. The obtained Ce-CaO solid adsorbent has a CO2 adsorption capacity that is almost the same as that in the first cycle after 15 cycles. Attached Figure Description

[0021] Figure 1 This is a SEM image of the Ce-CaO solid adsorbent obtained in Example 4 of the present invention;

[0022] Figure 2 This is the EDS diagram of the Ce-CaO solid adsorbent obtained in Example 4 of the present invention;

[0023] Figure 3 This is a test graph showing the CO2 adsorption performance of the Ce-CaO solid adsorbent obtained in Example 4 of this invention;

[0024] Figure 4 These are test graphs showing the CO2 adsorption performance of Ce-CaO solid adsorbents with different Ce content obtained in Examples 1-4 of this invention.

[0025] Figure 5 This is a test graph showing the CO2 adsorption performance of the Ce-CaO solid adsorbent prepared in Comparative Example 1 of Example 4 of the present invention. Detailed Implementation

[0026] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0027] Unless the context otherwise requires, the terms “comprising” and “including” in the specification and claims shall be understood as open-ended and inclusive, meaning “including, but not limited to”.

[0028] The terms "implementation," "an implementation," "another implementation," or "certain implementations" used in this specification refer to specific features, structures, or characteristics described in relation to the implementation, which are included in at least one implementation. Therefore, "implementation," "an implementation," "another implementation," or "certain implementations" do not necessarily all refer to the same implementation. Furthermore, specific features, structures, or characteristics can be combined in any way within one or more implementations. Each feature disclosed in this specification can be replaced by any alternative feature that provides the same, equivalent, or similar purpose. Therefore, unless otherwise specified, the disclosed features are merely general examples of equivalent or similar features.

[0029] The application will be further described in connection with the specific examples. It should be understood that these examples are only used to illustrate but not limit the scope of the application. The experimental methods in the following examples without specific conditions are generally according to the conventional conditions or according to the conditions suggested by the manufacturers. Unless otherwise specified, all percentages, ratios, proportions, or parts are by weight.

[0030] The unit of weight volume percentage in the present application is well known to those skilled in the art, for example, refers to the weight of solute in 100 milliliters of solution.

[0031] In the present application, the concentration unit "M" of the solution represents mol / L.

[0032] "One-pot method" refers to continuously performing multi-step reactions of reactants in one reactor without separation of intermediates, directly obtaining target substances.

[0033] The present application provides a preparation method of hollow microsphere structure calcium oxide-based CO2 adsorbent, comprising the following steps: S1) mixing glucose, soluble calcium salt and soluble cerium salt in water to obtain a mixed solution; S2) adding aqueous urea to the mixed solution, and after heating reaction, a solid substance is obtained; S3) calcining the solid substance to obtain a hollow microsphere structure calcium oxide-based CO2 adsorbent.

[0034] Among them, the present application does not have special restrictions on the source of all raw materials, which can be purchased on the market.

[0035] Mixing glucose, soluble calcium salt and soluble cerium salt in water to obtain a mixed solution; the molar ratio of glucose to calcium element in soluble calcium salt is preferably (2-2.1):1, more preferably 2:1; the soluble calcium salt can be any soluble calcium salt known to those skilled in the art without special restrictions, and in the present application, it preferably includes but is not limited to calcium nitrate; the soluble cerium salt can be any soluble cerium salt known to those skilled in the art without special restrictions, and in the present application, it preferably includes but is not limited to cerium nitrate; the molar ratio of cerium element in soluble cerium salt to calcium element in soluble calcium salt is preferably 0.005-0.1:1; in some embodiments provided by the present application, the molar ratio of cerium element in soluble cerium salt to calcium element in soluble calcium salt is specifically 0.1:1, 0.05:1, 0.02:1 or 0.005:1; by controlling the doping amount of Ce element, the hollow microsphere structure of the calcium oxide-based CO2 adsorbent can be ensured; the mixing is preferably carried out at room temperature; the mixing time is preferably 5-30 min, more preferably 10-20 min, and more preferably 15 min; the concentration of glucose in the mixed solution is preferably 1-3 mol / L, more preferably 1.5-2.5 mol / L, and more preferably 2-2.5 mol / L, and most preferably 2.25 mol / L.

[0036] The urea aqueous solution is added to the mixed solution, and solid substances are obtained after heating reaction; in the present application, the urea aqueous solution is preferably added dropwise to the mixed solution; the concentration of the urea solution is preferably 0.15-2 g / mL, more preferably 0.15-1 g / mL, again preferably 0.15-0.5 g / mL, again preferably 0.15-0.3 g / mL, and 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), and more preferably 1:5; the molar ratio of urea to calcium in the soluble calcium salt is preferably less than 0.55, more preferably 0.4-0.54, again preferably 0.45-0.54, again preferably 0.5-0.53, and most preferably 0.52-0.53; the addition of an appropriate amount of urea can maintain the appropriate alkalinity in the mixed solution, so that a part of CaCO3 is uniformly precipitated on the template and the desired morphology is formed, and can also promote the uniform distribution of calcium ions and cerium ions on the surface of the carbon sphere, and the carbonates formed by the hydrolysis of urea can also precipitate a part of calcium ions and cerium ions in the form of carbonates on the surface of the carbon sphere. Without urea, the simple addition of Ca(NO3)2 to the glucose solution and subsequent calcination of the product will produce a ring-shaped CaO structure, rather than the desired morphology. After the urea aqueous solution is added to the mixed solution, stirring is preferably performed, and then heating reaction is performed; the stirring time is preferably 1-10 min, more preferably 2-8 min, again preferably 4-6 min, and most preferably 5 min; the heating reaction temperature is preferably 165-175°C, and more preferably 170°C; the heating reaction time is preferably 15-30 h, more preferably 20-28 h, again preferably 22-26 h, and most preferably 24 h; and filtration is performed after heating reaction to obtain solid substances.

[0037] In the present application, CaCO3 is precipitated on the template while Ce is introduced, and under the alkaline conditions of the hydrolysis of an appropriate amount of urea, the amount of CaCO3 precipitated on the template is sufficient to form carbon spheres, so that the hollow microspherical morphology of the Ce-CaO adsorbent can be retained after subsequent calcination and other process treatments. Moreover, Ce can be better dispersed on the surface of the carbon sphere or in the pores. This process not only has the process of CaCO3 precipitating on the carbon sphere to form a carbon sphere, but also has the process of a part of Ca being adsorbed on the carbon sphere by electrostatic attraction and forming a hollow microspherical morphology together with the precipitated CaCO3 when being burned. Compared with the adsorbent obtained by impregnation of Ce into CaO hollow microspheres, the dispersion of Ce in the adsorbent obtained by impregnation is relatively uneven, and Ce has a greater impact on the lattice structure of Ca element during calcination, so that the original hollow microspherical morphology cannot be well retained, and thus the carbonization rate, adsorption capacity and service life of the adsorbent are adversely affected.

[0038] After calcination of the solid substance, a hollow microsphere structure calcium oxide-based CO2 adsorbent is obtained; in the present application, the solid substance is preferably washed with water and ethanol, dried, and then calcined; the temperature of the drying is preferably 60-100°C, more preferably 70-90°C, and even more preferably 80°C; the time of the drying is preferably 8-20h, more preferably 10-15h, and even more preferably 12h; the temperature of the calcination is preferably 750-850°C, more preferably 780-820°C, and even more preferably 800°C; within this range of calcination temperature, the template agent can be removed well, so that the adsorbent obtains a crystal structure and pore size that are favorable for adsorbing CO2; the time of the calcination is preferably 0.5-2h, more preferably 0.8-1.5h, and even more preferably 1h; during the calcination process, the heating rate from room temperature to the calcination temperature is controlled within a certain range, and the heating rate also affects the structure and morphology of the microspheres. A faster heating rate can result in uneven performance on the surface of the microspheres, while a slower heating rate can promote uniform growth inside the microspheres, which is not conducive to the formation of hollow microspheres. In the present application, the heating rate of the calcination is preferably 3-6°C / min, more preferably 4-6°C / min, and even more preferably 5°C / min. Through the control of the heating rate and the calcination temperature in the above-mentioned calcination process, the Ce-CaO hollow porous microspheres are obtained, and the pore distribution is uniform, thereby improving the CO2 adsorption capacity. If the pore distribution inside the microspheres is not uniform, some parts of the pores can be too small to fully adsorb CO2 molecules, thereby resulting in a decrease in the CO2 adsorption capacity.

[0039] In the present application, the adsorbent is prepared by "one-pot method", and during the heating process, glucose forms carbon spheres, the interior of the carbon spheres has certain pores, and the surface has certain hydrophilic groups. A part of the calcium ions and cerium ions enter the interior of the carbon spheres, and a part of them adhere to the surface of the carbon spheres through the hydrophilic groups. Then, under the action of urea, the overall system is in a proper alkaline environment, which is conducive to the uniform distribution of the calcium ions and cerium ions on the surface of the carbon spheres. In addition, the carbonates formed by the hydrolysis of urea can also make a part of the calcium ions and cerium ions precipitate in the form of carbonates on the surface of the carbon spheres. When the template agent is removed by high-temperature calcination, the metal ions in the interior and on the surface of the carbon spheres can better interact to form a hollow microsphere morphology. This morphology is conducive to the diffusion of CO2, thereby significantly improving the adsorption capacity and adsorption rate. In addition, the hollow volume inside the hollow microspheres can adapt to the volume change during the reaction process, and has a certain anti-sintering ability. At the same time, the doping of cerium elements can reduce the particle size of calcium oxide, and well-dispersed cerium oxide can also play a barrier role, effectively preventing the growth and sintering of calcium oxide microcrystals, thereby making the adsorbent exhibit excellent stability. The doping of cerium oxide also improves the carbonation rate of the adsorbent, thereby obtaining a higher adsorption capacity in a short time.

[0040] The application further provides the hollow microspherical structure calcium oxide-based CO2 adsorbent prepared by the preparation method.

[0041] The application further provides application of the hollow microspherical structure calcium oxide-based CO2 adsorbent prepared by the preparation method in adsorbing CO2.

[0042] In order to further illustrate the application, the application provides a hollow microspherical structure calcium oxide-based CO2 adsorbent and a preparation method thereof in the following combined with examples.

[0043] The reagents used in the following examples are all commercially available.

[0044] Example 1

[0045] 6.10 g of glucose, 4.0 g of calcium nitrate tetrahydrate and 0.7375 g of cerium nitrate hexahydrate were weighed into a beaker, 15 mL of deionized water was added into the beaker, and stirring was performed for 15 minutes to obtain a first solution. 0.54 g of urea was dissolved in 3 mL of deionized water to obtain a second solution. The second solution was added dropwise into the first solution, and stirring was performed for 5 minutes to obtain a third solution. The third solution was placed into a reaction kettle, and reaction was performed at 170℃ for 24 hours. After that, suction filtration was performed to obtain a solid substance.

[0046] The solid substance was first washed with 2000 mL of deionized water, and then washed with 500 mL of ethanol. The filtered solid sample was placed into an 80℃ oven for drying for 12 hours. The dried sample was taken out, ground into a powder, and then calcined. The calcination process was as follows: calcination was performed at 800℃ with a temperature increasing rate of 5℃ / min for 1 hour to obtain a Ce-stabilized CaO-based solid adsorbent, and the sample was named as Ca3M-10Ce.

[0047] Example 2

[0048] 6.10 g of glucose, 4.0 g of calcium nitrate tetrahydrate and 0.7375 g of cerium nitrate hexahydrate were weighed into a beaker, 15 mL of deionized water was added into the beaker, and stirring was performed for 15 minutes to obtain a first solution. 0.54 g of urea was dissolved in 3 mL of deionized water to obtain a second solution. The second solution was added dropwise into the first solution, and stirring was performed for 5 minutes to obtain a third solution. The third solution was placed into a reaction kettle, and reaction was performed at 170℃ for 24 hours. After that, suction filtration was performed to obtain a solid substance.

[0049] The solid material was first washed with 2000 mL of deionized water, then washed with 500 mL of ethanol, and the filtered solid sample was placed in an oven at 80 °C for 12 hours to dry. The dried sample was removed, ground into a powder, and calcined. The calcination process was to heat at a rate of 5 °C / min to 800 °C for 1 hour to obtain a Ce-stabilized CaO-based solid sorbent, which was named Ca3M-5Ce.

[0050] Example 3

[0051] In a beaker, 6.10 g of glucose, 4.0 g of calcium nitrate tetrahydrate, and 0.1471 g of cerium nitrate hexahydrate were weighed, 15 mL of deionized water was added, and stirred for 15 minutes to obtain a first solution. 0.54 g of urea was dissolved in 3 mL 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 a temperature of 170 °C for 24 hours, and then filtered to obtain a solid material.

[0052] The solid material was first washed with 2000 mL of deionized water, then washed with 500 mL of ethanol, and the filtered solid sample was placed in an oven at 80 °C for 12 hours to dry. The dried sample was removed, ground into a powder, and calcined. The calcination process was to heat at a rate of 5 °C / min to 800 °C for 1 hour to obtain a Ce-stabilized CaO-based solid sorbent, which was named Ca3M-2Ce.

[0053] Example 4

[0054] In a beaker, 6.10 g of glucose, 4.0 g of calcium nitrate tetrahydrate, and 0.1471 g of cerium nitrate hexahydrate were weighed, 15 mL of deionized water was added, and stirred for 15 minutes to obtain a first solution. 0.54 g of urea was dissolved in 3 mL 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 a temperature of 170 °C for 24 hours, and then filtered to obtain a solid material.

[0055] The solid material was first washed with 2000 mL of deionized water, then washed with 500 mL of ethanol, and the filtered solid sample was placed in an oven at 80 °C for 12 hours to dry. The dried sample was removed, ground into a powder, and calcined. The calcination process was to heat at a rate of 5 °C / min to 800 °C for 1 hour to obtain a Ce-stabilized CaO-based solid sorbent, which was named Ca3M-2Ce.

[0056] Comparative Example 1

[0057] This comparative example was prepared by a two-step method:

[0058] Firstly, the preparation of CaO-based adsorbent without Ce doping: 6.10 g of glucose and 4.0 g of calcium nitrate tetrahydrate were weighed in a beaker, 15 mL of deionized water was added to the beaker, and the mixture was stirred for 15 minutes to obtain a first solution. 0.54 g of urea was dissolved in 3 mL of deionized water to obtain a second solution. The second solution was added dropwise to the first solution, and the mixture was stirred for 5 minutes to obtain a third solution. The third solution was placed in a reaction kettle and reacted at a temperature of 170°C for 24 hours, after which the solid material was obtained by filtration.

[0059] The solid material was first washed with 2000 mL of deionized water, then washed with 500 mL of ethanol, and the filtered solid sample was placed in an oven at 80°C for drying for at least 12 hours. The dried sample was taken out, ground into powder, and then calcined. The calcination process: calcination at 800°C for 1 hour with a heating rate of 5°C / min to obtain a CaO-based solid adsorbent. This sample is named Ca3M.

[0060] Then Ce was introduced by impregnation: 0.5 g of Ca3M was weighed, 0.00638 g of cerium nitrate hexahydrate was added, 10 g of deionized water was added, and the mixture was stirred at room temperature for 12 hours. Then the water was evaporated while stirring at 90°C, and the mixture was dried at 130°C for 12 hours. After drying, the mixture was placed in a programmed temperature muffle furnace and calcined at 500°C for 2 hours with a heating rate of 2°C / min. The obtained sample is denoted as Ca3M-5Ce-imp.

[0061] The Ce-CaO solid adsorbent prepared in Example 4 was analyzed by a scanning electron microscope (SEM) of Japanese Electronics type JSM-7900F (as shown in Figure 1 ), and the morphology of the adsorbent was tested under test conditions of an acceleration voltage of 2 kV, and the elements on the surface of the sample were analyzed by EDS. Preparation before testing: conductive tape was attached to the sample holder, then the sample powder was evenly placed on the conductive tape, then the sample powder that was not stuck was blown away with compressed air, then a heavy metal plating operation was performed to ensure conductivity, and finally the scanning test was performed. The results showed that the adsorbent with a Ce doping amount of 0.5% maintained a spherical morphology, as shown in Figure 2 The results of the X-ray energy spectrometer (EDS) showed that Ce was successfully introduced and uniformly distributed on the surface of the microspheres, as shown in Figure 2 .

[0062] The CO2 adsorption performance of the Ce-CaO solid adsorbent prepared in Example 4 was tested using a Mettler Toledo TGA / DSC 3+ thermogravimetric analyzer. Less than 10 mg of adsorbent was placed on an alumina crucible for each test. At the beginning of each adsorption process, the sample was held at 850°C for 30 minutes under 100 vol% N2. The adsorption process was then carried out at 650°C for 30 minutes under a 15 vol% CO2 / 85 vol% N2 atmosphere. The desorption process was carried out at 850°C and 85 vol% N2 for 10 minutes. The heating and cooling rates were maintained at 20°C / min. The results were found (see Appendix). Figure 3 The adsorbent with a Ce doping content of 0.5% exhibited the optimal adsorption capacity and the best cycling stability. After 15 cycles, the CO2 adsorption capacity remained at 8.56 mmol·g⁻¹. -1 8.92 mmol·g in the first cycle -1 They are almost identical.

[0063] In addition, the CO2 adsorption performance of Ce-CaO solid adsorbents with different Ce doping amounts in Examples 1-4 was tested, and the methods were as described above, with the results shown in the appendix. Figure 4 .Depend on Figure 4 It can be seen that the Ce-CaO solid adsorbent prepared in Example 4 has a very high adsorption capacity.

[0064] The CO2 adsorption performance of the Ce-CaO solid adsorbents prepared in Example 4 and Comparative Example 1 was tested. The specific experimental methods are as described above. The results are attached. Figure 5 The results show that the adsorption capacity of Ce-CaO solid adsorbent prepared by the impregnation method is significantly lower than that of Ce-CaO solid adsorbent prepared by the one-pot method. Firstly, in the adsorbent prepared by the impregnation method, cerium has poor dispersion and occupies adsorption sites; secondly, the impregnation method destroys the original structure of CaO.

Claims

1. A method for preparing a hollow microspherically structured calcium oxide-based CO2 adsorbent, characterized by, The method comprises the following steps: S1) mixing glucose, soluble calcium salt and soluble cerium salt in water to obtain a mixed solution; S2) adding an aqueous urea solution to the mixed solution, and obtaining a solid substance after heating reaction; S3) calcining the solid substance to obtain a hollow microsphere structure calcium oxide-based CO2 adsorbent; the heating rate of the calcination is 3-6 ℃ / min.

2. The production method according to claim 1, characterized by, 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 production method according to claim 1, characterized by, The molar ratio of urea to calcium in the soluble calcium salt is less than 0.

55.

4. The method of 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, characterized in that, The concentration of the urea solution is 0.15-2 g / mL; the volume ratio of the aqueous urea solution to the mixed solution is 1:(4.5-5.5).

6. The method of claim 1, wherein, The heating temperature in the step S2) is 165-175 ℃; the heating time is 15-30 h.

7. The preparation method according to claim 1, characterized in that, The calcination temperature in the step S3) is 750-850 ℃; the calcination time is 0.5-2 h.

8. The hollow microsphere structure calcium oxide-based CO2 adsorbent prepared by the preparation method in any one of claims 1-7.

9. The application of the hollow microsphere structure calcium oxide-based CO2 adsorbent prepared by the preparation method in any one of claims 1-7 in adsorbing CO2.

Images