Calcium-based CO2 adsorbent as well as preparation method and application thereof

Abstract

The invention provides a calcium-based CO2 adsorbent as well as a preparation method and application thereof, and relates to the technical field of calcium-based adsorbents. The adsorbent is prepared by performing ultrasonic pickling on the carbide slag and doping one or more metal elements of Ce, Mg, Zr and Mn, preferably, the Ce element is doped, and the effect is optimal when the doping proportion of CeO2 is 10-15%. According to the adsorbent prepared by adopting the preparation method provided by the invention, due to the introduction of the metal oxide with high tower temperature, the pore structure of the adsorbent is obviously improved, CaO particles can be effectively anchored and isolated by an interfacial effect formed by the metal oxide and CaO, and the reaction activity of the adsorbent is enhanced; in the cyclic CO2 trapping process, the sintering resistance characteristic and the cyclic trapping performance are remarkably improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of calcium-based adsorbent, in particular to a calcium-based CO2 adsorbent and a preparation method and application thereof. BACKGROUND

[0002] Based on the reversible reaction CaO+CO2<->CaCO3, the calcium cycle technology has the advantages of high theoretical CO2 capture capacity, low raw material cost, and easy disposal of waste adsorbent, and is considered as one of the most potential carbon capture technologies for large-scale industrial application. This kind of technology usually takes CaO-based material as the core component of the dual functional material, and its adsorption performance is crucial. The preparation of CaO adsorbent from calcium-containing industrial solid waste has both environmental and economic benefits. Among many solid wastes, the active calcium-containing solid waste represented by carbide slag has a high resource utilization value because its main component is Ca(OH)2 and can be directly used in the calcium cycle process. However, carbide slag itself has inherent defects such as small specific surface area and poor pore structure, which leads to low CO2 capture capacity of the derived CaO adsorbent and insufficient cycle stability, making it difficult to meet the long-term operation requirements.

[0003] In order to improve the performance of CaO adsorbent, various modification strategies are disclosed in the prior art, including hydration activation, metal element doping, and acid treatment. Among them, acetic acid treatment can effectively dissolve impurities and improve the pore structure of the material. However, the conventional liquid immersion method is limited by diffusion, and the modifier is difficult to penetrate uniformly into the particle interior, resulting in limited performance improvement. By introducing ultrasonic assisted technology, the cavitation effect and mass transfer enhancement can promote the deep penetration of acetic acid solution into the particle interior, more effectively expand the pore and activate the pore, thereby significantly improving the CO2 capture capacity. However, the adsorbent modified by such method still has capacity decay and cycle stability to be further improved due to the sintering and agglomeration of CaO grains during long-term high-temperature cycle operation.

[0004] Therefore, it is necessary to design an improved calcium-based CO2 adsorbent and a preparation method and application thereof to solve the above problems. SUMMARY

[0005] The present application aims to provide a calcium-based CO2 adsorbent and a preparation method and application thereof.

[0006] To achieve the above-mentioned application purposes, in a first aspect, the present application provides a preparation method of a calcium-based CO2 adsorbent, comprising the following steps:

[0007] After dissolving the metal oxide precursor in the acid solution, the calcium-based alkaline industrial solid waste is added, and the obtained mixture is acidified and modified under ultrasonic conditions. The calcium-based CO2 adsorbent is prepared after the ultrasonic treatment is completed;

[0008] The metal oxide precursor is at least one of cerium nitrate, manganese nitrate, magnesium nitrate, and zirconium nitrate.

[0009] Preferably, the calcium-based alkaline industrial solid waste is carbide slag, and the mass percentage of the metal oxide in the calcium-based CO2 adsorbent is 5-30%.

[0010] Preferably, the acid solution is an acetic acid solution with a mass percentage of 10%.

[0011] Preferably, the conditions of the ultrasonic process are as follows: power is 200 W, frequency is 40 kHz, and temperature is 60 DEG C.

[0012] In a second aspect, the present application provides a calcium-based CO2 adsorbent, wherein the mass percentage of CaO in the calcium-based CO2 adsorbent is 70-95%, the specific surface area is 9-13 m 2 / g, the total pore volume is 0.04-0.05 cm 3 / g, and the average pore size is 17-20 nm.

[0013] In a third aspect, the present application provides a use of a calcium-based CO2 adsorbent in CO2 capture.

[0014] The present application has the following beneficial effects:

[0015] 1. By doping metal oxides (especially CeO2) with high Tammann temperature, a uniformly dispersed inert skeleton can be constructed in the CaO matrix. This skeleton can effectively isolate CaO particles during high-temperature cycling, physically blocking their mutual contact and agglomeration, thereby significantly slowing down the decrease in specific surface area and the collapse of pore structure caused by sintering. Experimental data show that after 20 harsh carbonation / calcination cycles, the carbonation conversion rate of the adsorbent after optimized doping can still reach as high as 83.37%, and the deactivation rate can be as low as 2.1%, exhibiting excellent long-term cycling stability and solving the problem of rapid deactivation of CaO-based adsorbents due to sintering.

[0016] 2. By precisely controlling the type and ratio of doping elements, the cycling stability can be improved without losing too much initial capacity, breaking through the technical defect of traditional modification techniques that it is difficult to achieve both "initial capacity" and "cycling stability".

[0017] 3. Using industrial solid waste carbide slag as the main raw material, through the modification process of ultrasonic acid washing and controllable doping, it is converted into a high-performance CO2 adsorbent. This process not only realizes "waste treatment with waste", reduces the environmental burden of solid waste, but also greatly reduces the raw material cost of the adsorbent (compared with using high-purity calcium carbonate or calcium hydroxide). At the same time, the modification process conditions are mild and the process is simple, which has good industrial amplification potential and economic feasibility.

[0018] 4. The performance of the adsorbent is optimized by the cooperation of ultrasonic-assisted acid pickling and metal doping process. The ultrasonic-assisted acid pickling process can effectively remove impurities in the calcium carbide slag, and significantly improve the pore structure and specific surface area thereof, thereby providing rich mass transfer channels and active interfaces for subsequent reactions; and the doping modification effectively solves the stability problem caused by high-temperature sintering of the CaO-based adsorbent, and finally the adsorbent with excellent performance is prepared. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 XRD patterns of the calcium-based CO2 adsorbents prepared in Examples 1 to 4 of the present application and Ca100;

[0020] Figure 2 SEM patterns of the calcium-based CO2 adsorbents prepared in Examples 1 to 4 of the present application and Ca100;

[0021] Figure 3 Pore structure characteristics and specific surface area analysis results of the calcium-based CO2 adsorbents prepared in Examples 1 to 4 of the present application and Ca100;

[0022] Figure 4 CO2 capture performance test results of the calcium-based CO2 adsorbents prepared in Examples 1 to 4 of the present application and Ca100;

[0023] Figure 5 Reaction rate diagrams of the calcium-based CO2 adsorbents prepared in Examples 1 to 4 of the present application and Ca100 under initial cycles;

[0024] Figure 6 CO2 capture performance results of the adsorbents under different CeO2 doping amounts in Example 1 and Examples 5 to 6 of the present application;

[0025] Figure 7 Reaction rate diagrams of the adsorbents under different CeO2 doping amounts in Example 1 and Examples 5 to 6 of the present application under initial cycles. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical scheme and advantages of the present application clearer, the present application will be described in detail below in combination with the drawings and specific embodiments.

[0027] Here, it also needs to be explained that, in order to avoid the obscuring of the present application due to unnecessary details, only the structures and / or processing steps closely related to the scheme of the present application are shown in the drawings, and other details not closely related to the present application are omitted.

[0028] It is also to be noted that the terms "comprising", "including", or any other variant thereof are intended to cover a non-exclusive inclusion, such that processes, methods, articles, or apparatuses that comprise, include, or are otherwise characterized as including a list of elements do not include only those elements recited but also other elements not expressly listed or inherent to such processes, methods, articles, or apparatuses.

[0029] Referring to Figure 1 The preparation method of the calcium-based CO2 adsorbent provided by the present application comprises the following steps:

[0030] After the metal oxide precursor is dissolved in the acidic solution, the calcium-based alkaline industrial solid waste is added, and the obtained mixture is modified by acidification under ultrasonic conditions. After the ultrasonic treatment is completed, the obtained solid product is dried to obtain the calcium-based CO2 adsorbent, which has a specific surface area (S BET ) of 9-13 m 2 / g, a total pore volume (V total ) of 0.04-0.05 cm 3 / g, and an average pore size of 17-20 nm. The mass fraction of the metal oxide in the calcium-based CO2 adsorbent is 5-30%.

[0031] In some embodiments, the metal oxide precursor is at least one of cerium nitrate, manganese nitrate, magnesium nitrate, and zirconium nitrate.

[0032] In some embodiments, the acidic solution is specifically an acetic acid solution, and the mass fraction of the acetic acid solution is 10%.

[0033] In some embodiments, the ultrasonic treatment is performed under the following conditions: a power of 200 W, a frequency of 40 kHz, and a temperature of 60°C.

[0034] In some embodiments, the calcium-based alkaline industrial solid waste is an industrial solid waste whose main component is calcium hydroxide, and is preferably carbide slag, which has a Ca(OH)2 mass content of ≥80%, a silicon dioxide content of ≤5%, and an aluminum oxide content of ≤3%.

[0035] The calcium-based CO2 adsorbent provided by the present application, the preparation method thereof, and the application thereof are further limited as follows by combining specific embodiments:

[0036] Embodiment 1

[0037] The present embodiment provides a preparation method of a calcium-based CO2 adsorbent, which comprises the following steps:

[0038] After 1 g of cerium nitrate is dissolved in 75 mL of a 10% mass percentage acetic acid solution, 6 g of carbide slag is added, and the obtained mixture is subjected to ultrasonic acid pickling vibration at 200 W, 40 kHz, and 60°C for 1 h to modify the carbide slag by doping, and after the acid pickling is completed, the obtained solid sample is dried at 80°C to obtain a calcium-based CO2 adsorbent, which is denoted as Ca90Ce10, indicating that the mass percentage of CaO in the calcium-based CO2 adsorbent is 90%, and the mass percentage of CeO2 is 10%. It should be noted that, unless otherwise specified, the raw materials used in the examples of the present application can be obtained by market purchase. In actual application, the calcium-based CO2 adsorbent can be ground and sieved into 40-60 mesh before use according to the application requirements.

[0039] Example 2

[0040] Example 2 differs from Example 1 only in that the metal oxide precursor is magnesium nitrate, and the remaining experimental parameters are the same as those of Example 1, which will not be repeated here. The obtained calcium-based CO2 adsorbent is denoted as Ca90Mg10.

[0041] Example 3

[0042] Example 3 differs from Example 1 only in that the metal oxide precursor is zirconium nitrate, and the remaining experimental parameters are the same as those of Example 1, which will not be repeated here. The obtained calcium-based CO2 adsorbent is denoted as Ca90Zr10.

[0043] Example 4

[0044] Example 4 differs from Example 1 only in that the metal oxide precursor is manganese nitrate, and the remaining experimental parameters are the same as those of Example 1, which will not be repeated here. The obtained calcium-based CO2 adsorbent is denoted as Ca90Mn10.

[0045] The XRD patterns of the calcium-based CO2 adsorbents prepared in Examples 1-4 and Ca100 (CaO content is 100%) are shown in Figure 1 The results show that the CaO content in the five catalysts is the highest, which is mainly because the main component of carbide slag is Ca(OH)2, and a large amount of calcium acetate is generated after acetic acid pickling. After calcination at high temperature, a large amount of CaO is formed. By comparing the adsorbents doped with Ce, Zr, Mg, and Mn elements, it can be found that the doped metal elements can be divided into two categories. One category is Zr and Mn elements that can easily react with CaO to form complex phases CaZr4O9 and CaMnO3; the other category is Ce and Mg elements that are not easy to react with CaO and only form simple metal oxides. This is mainly because the doping of Zr and Mn elements belongs to reactive doping, and Zr 4+ and Mn 4+With a small ionic radius, it can easily and quickly enter the CaO lattice to react and form a CaZr4O9 and CaMnO3 composite phase; the doping of Ce and Mg elements is an inert dispersed doping type. 4+ and Mg 2+ The ionic radius of MgO is relatively large, making it difficult for it to enter the CaO lattice in large quantities and react. It mainly exists in the form of metal oxides CeO2 and MgO. Furthermore, the mechanisms by which reactive doping and inert dispersion doping affect the cycle stability of CaO differ significantly. Reactive doping achieves grain locking by generating a composite phase, which helps suppress sintering, while inert dispersion doping achieves interface confinement through physical isolation, enhancing the ability to retain the pore structure. In addition, the figure shows that with the doping of metal elements Ce, Zr, Mg, and Mn, the signal peak attributable to CaO shifts to the right from 2θ=37.41º to 37.61º, 37.59º, 37.50º, and 37.59º. This is mainly because the doping of metal elements causes different degrees of lattice contraction. The contraction caused by Zr and Mn doping mainly replaces part of CaO. 2+ This leads to a decrease in lattice parameters; while CeO2 and MgO generated by doping with Mg and Ce are mostly uniformly distributed at the CaO grain boundaries or surface, which will form an external compressive stress field, causing microscopic shrinkage of CaO unit cells.

[0046] SEM images of the calcium-based CO2 adsorbents and Ca100 prepared in Examples 1 to 4 are shown below. Figure 2 As shown, where, Figure 2 Figures (a1)-(a2) show Ca100 at different magnifications. Figure 2 Figures (b1)-(b2) show Ca90Ce10 at different magnifications. Figure 2 Figures (c1)-(c2) show Ca90Mg10 at different magnifications. Figure 2 Figures (d1)-(d2) in the figure show Ca90Zr10 at different magnifications. Figure 2 Figures (e1)-(e2) show Ca90Mn10 at different magnifications. The results show that the adsorbents prepared in Examples 1 to 4 exhibit obvious loose and porous structural characteristics. This is mainly because acetic acid washing dissolves some of the Ca. 2+ Ions are generated to form calcium acetate, which decomposes upon high-temperature calcination, releasing gases such as CO2 and water vapor. This enriches the pore structure of the adsorbent. Secondly, the ultrasonic cavitation effect brought about by ultrasonic acid washing generates instantaneous high-pressure microjets, which impact the particle surface, promoting the propagation of cracks in the adsorbent and opening potential pores. Further observation is needed. Figure 2It can be found that the loose degree and connectivity of the pore structure of the five adsorbents are different due to the existence of different elements. Specifically, Ca100 exhibits a dense blocky morphology, which is mainly because the particles are severely aggregated, the number of internal pore channels is small, the pore structure stability is insufficient, and the sintering tendency is relatively strong; The accumulation of Ca90Ce10 and Ca90Mg10 adsorbent particles becomes significantly loose, forming a large number of continuous lamellar and channel-shaped open pores, the pore wall is thin, and the pore connectivity is good; Ca90Zr10 and Ca90Mn10 adsorbents exhibit relatively thick lamellar and shrinkage pore structure, although they still have certain porosity, but the passivation degree of particle edge is higher, and the pore structure is more compact.

[0047] The pore structure characteristics and specific surface area analysis results of the calcium-based CO2 adsorbents prepared in Examples 1 to 4 and Ca100 are shown in FIGS. (a) and (b) of Figure 3 , Figure 3 FIG. (a) is the nitrogen adsorption-desorption isotherm of the five adsorbents, Figure 3 FIG. (b) is the pore size distribution graph of the five adsorbents, the results show that the isothermal adsorption curves of the five adsorbents are type III adsorption curves, accompanied by H3 hysteresis loop in the relative pressure range of 0.8-1.0, type III isotherm usually indicates that the interaction between the adsorbate and the surface of the adsorbent is weak, and the gas-solid phase interaction mainly depends on the physical adsorption dominated by weak van der Waals force. The existing H3 type hysteresis loop further indicates that the pore structure of the sample is mainly composed of slit-shaped or lamellar mesopores formed by the accumulation of irregular CaO nanoparticles, and does not contain obvious closed pores or regular pore channel structure. Such pores are generally derived from the accumulation gap between irregular CaO nanoparticles, showing a wide pore size distribution and good pore connectivity. It is worth noting that there is no obvious adsorption platform in the type III isotherm, which means that the proportion of micropores in the pore structure is low, and the mesopores and macropores are dominant. This has a dual impact on CO2 capture: on the one hand, mesopores and macropores help to reduce mass transfer resistance and delay the diffusion control effect caused by particle densification; on the other hand, the lack of micropores means that the specific surface area contribution is limited, which may affect the initial carbonation rate and reaction depth. The pore structure data of the adsorbents is shown in Table 1, the results show that,

[0048] Compared with Ca100 adsorbent, the specific surface area of the adsorbents after ultrasonic doping modification is slightly improved, from 8.52 m 2 / g to 12.22 m 2 / g, 12.20 m 2 / g, 10.37 m 2 / g, and 9.13 m 2The specific surface area of ​​Ca90Ce10 and Ca90Mg10 increased most significantly, indicating that the introduction of Ce and Mg can effectively promote the formation of a looser packing structure between particles, increase the degree of pore exposure, and thus significantly improve the CO2 mass transfer channels. In terms of total pore volume, Ca90Mg10 had the largest total pore volume, at 0.079 cm³ / g. 3 The pore volume of the Mg-doped sample was significantly higher than that of other samples, indicating that Mg doping is more effective in forming open pores, which helps alleviate pore blockage during carbonate formation. In contrast, the pore volume of the Mn-doped sample was the lowest, at 0.041 cm³. 3 The / g indicates that the introduction of Mn makes particle aggregation more likely, resulting in a slightly denser pore structure. Furthermore, the average pore size of all samples is in the 17-30 nm range, which is typical of mesopore-macropore structures. Notably, after Ce doping, the average pore size significantly decreased from 30.29 nm to 17.57 nm, indicating that CeO2 dispersed and filled some of the interparticle channels, making the pore size distribution more concentrated in the mesopore region.

[0049] Table 1. Pore structure data of calcium-based CO2 adsorbents and Ca100 prepared in Examples 1 to 4.

[0050]

[0051] Furthermore, the CO2 capture performance of the aforementioned calcium-based CO2 adsorbent was investigated during the experiment. Performance testing was conducted on a thermogravimetric analyzer (TGA, Pyris 1) by monitoring the mass change of the adsorbent with temperature and time. The adsorbent was first heated from 50℃ to 650℃ at a rate of 10℃ / min under N2 atmosphere. Upon reaching 650℃, the adsorbent was calcined under N2 for 30 minutes. After calcination, the reaction atmosphere was switched to 15% CO2, and the adsorbent underwent CO2 capture for 30 minutes. After capture, the reaction atmosphere was switched back to N2, and the adsorbent underwent calcination for another 30 minutes. The above capture and calcination experiments were repeated 20 times to test the cyclic stability and CO2 adsorption capacity (C2) of the adsorbent. n The formula for calculating (%) is as follows: , where m n The adsorbent deactivation rate (S0) represents the mass after adsorption, and m0 represents the mass before adsorption. n The formula for calculating (%) is as follows: Where C1 represents the CO2 capture capacity of the first cycle, C n This formula represents the CO2 capture capacity in the nth cycle and can accurately quantify the cyclic capture performance of the adsorbent.

[0052] The test results of CO2 capture performance are as follows: Figure 4 As shown, where, Figure 4Figure (a) shows the CO2 adsorption capacity decay curve after multiple cycles. Figure 4 Figure (b) shows the carbonation conversion rate decay curves after multiple cycles. The results show that among the five adsorbents, Ca100 adsorbent has the strongest initial CO2 capture performance, with a CO2 capture capacity of 0.74 g / g and a carbonation conversion rate of 94.35%. However, when doped with Ce, Mg, Zr, and Mn elements, the CO2 capture capacity of the adsorbent decreases to 0.64 g / g, 0.57 g / g, 0.54 g / g, and 0.61 g / g, respectively, and the carbonation conversion rates are 90.82%, 81.04%, 77.58%, and 86.07%, respectively. This indicates that the doping of metal elements leads to a decrease in the CO2 capture performance of the adsorbent in the initial cycle. This is mainly because the inert supports (CeO2, MgO, CaZr4O9, and CaMnO3) introduced during the doping process do not participate in the carbonation reaction between CaO and CO2, thereby diluting the effective CaO content in the adsorbent. The presence of these inert supports reduces the number of reactive active sites per unit mass of adsorbent, directly leading to a decrease in the initial CO2 capture capacity of the adsorbent. Simultaneously, oxides formed by doping with metal elements are typically distributed within the pore channels of the CaO adsorbent during calcination, making it difficult for CO2 molecules to diffuse rapidly to the active sites inside the CaO during the initial reaction stage. In particular, oxides such as Ce, Zr, and Mn are distributed at the nanoscale within the pore channels, maintaining close contact with CaO and increasing the diffusion resistance of CO2, thereby reducing the initial carbonation reaction rate.

[0053] Furthermore, after 20 cycles, the CO2 capture capacity of the five adsorbents decreased by 0.14 g / g, 0.05 g / g, 0.04 g / g, 0.05 g / g, and 0.06 g / g, respectively, with deactivation rates of 19.21%, 7.65%, 6.50%, 8.55%, and 10.47%. This indicates that the pure CaO adsorbent has poor anti-sintering performance, and its adsorption capacity decreases significantly with increasing cycle number. This is mainly because the Taman temperature of CaCO3 is approximately 533℃, while the adsorption-desorption reaction of the adsorbent takes place at 650℃. The higher reaction temperature causes sintering of the adsorbent, leading to an irreversible decrease in specific surface area and pore structure, thus increasing the diffusion resistance of CO2. When doped with Ce, Mg, Zr, and Mn metal elements, the adsorbent contains uniformly distributed inert supports such as CeO2, MgO, CaZr4O9, and CaMnO3. These substances have high Taman temperatures, which can effectively isolate CaO adsorbent particles and slow down the sintering of the adsorbent.

[0054] Further observation Figure 4It can be seen that Ca90Ce10 always maintains a high CO2 capture performance, and after 20 cycles, the carbonation conversion rate of the adsorbent is the highest, reaching 83.87%, and after 10 cycles, the CO2 capture capacity of the adsorbent appears a slight rebound, which is mainly related to the synergistic effect of structure reconstruction and interface activation. During the cycle process, the good oxidation-reduction characteristics of CeO2 nanoparticles make the oxygen vacancies dynamically generate and migrate, which are uniformly distributed in the CaO adsorbent to improve the reaction activity of the interface area, and part of the collapsed pore is reopened to form a new pore structure, thereby improving the pore structure of the adsorbent. With the gradual stabilization of the CaO-CeO2 interface, the adsorption and reaction activation capacity of CO2 slightly increases, so a slight rebound in the adsorption capacity is observed after 10 cycles.

[0055] The reaction rate diagram of the five adsorbents under the initial cycle is shown in Figure 5 It can be found that the carbonation rate of Ca100 and Ca90Mg10 is higher than that of Ca90Ce10, Ca90Zr10 and Ca90Mn10, which further indicates that the doping of Ce, Zr and Mn will be distributed in the pore channel of the adsorbent, thereby reducing the initial carbonation reaction rate.

[0056] Examples 5 to 6

[0057] Examples 5 to 6 and Example 1 only differ in that the amount of CeO2 doping is different from Example 1. Specifically, in Example 5, the amount of CeO2 doping is 5%, and the obtained adsorbent is recorded as Ca95Ce5, and in Example 6, the amount of CeO2 doping is 15%, and the obtained adsorbent is recorded as Ca85Ce15.

[0058] The CO2 capture performance results of the adsorbents in Example 1 and Examples 5 to 6 with different amounts of CeO2 doping are shown in Figure 6 Figure 6 Figure (a) in Figure 6 ​Figure (b) in the above table is the corresponding carbonation conversion results, which show that with the increase of Ce02doping amount, the initial CO2capture capacity of CaO sorbents decreases from 0.74 g / g to 0.56 g / g, 0.64 g / g and 0.57 g / g, while Ca95Ce5, as the doped modified sorbent with the highest active CaO content, has the worst initial CO2capture performance, with a carbonation conversion of only 75.08%, which is significantly lower than the 94.35%, 90.82 and 84.64% of the rest of the sorbents. This is probably because the low content of Ce02mainly distributed in the pore channels of the sorbent causes the decrease of the initial CO2capture capacity of the sorbent. At a 5 wt% doping level, Ce02nanoparticles are highly dispersed in the pore channels of the CaO sorbent, shielding a large number of originally accessible CO2active sites of CaO, hindering the rapid mass transfer of CO2, resulting in a decrease in the initial adsorption rate and conversion. On the contrary, when the Ce02content increases to 10-15 wt%, Ce02tends to form independent dispersed particles and play a "support-isolation" role at the grain boundary, effectively inhibiting CaO grain sintering and maintaining the pore channels of the sorbent.

[0059] In addition, Figure 6 It is also shown that the CO2capture performance of Ca95Ce5will increase first and then decrease with the increase of the number of cycles, while the other three sorbents show a gradually decreasing trend. Secondly, with the progress of the cycle, the adsorption capacity of Ca95Ce5increases from the initial 0.56 g / g to 0.62 g / g (12th cycle), and then rapidly decreases to 0.54 g / g, which is mainly because there are phenomena of Ce02distribution in the pore channels of the sorbent, pore structure reconstruction and CaO sintering during the process of Ca95Ce5sorbent capturing CO2. Low content of Ce02initially highly dispersed in the pore channels of the CaO sorbent, covering part of the active CaO sites, limiting and hindering the mass transfer and diffusion of CO2and the carbonation reaction with active CaO, thus showing a lower initial CO2adsorption capacity. With the progress of the cycle reaction, the sorbent can promote the re-exposure of the sorbent channels under the characteristics of the rich oxygen vacancies of Ce02, and the support and isolation effect of Ce02inhibits the sintering of CaO particles, so that the adsorption capacity appears a temporary rebound in the middle period. With the continuation of the cycle, irreversible processes such as sintering, particle growth and product layer densification gradually dominate, leading to irreversible reduction of pore volume and specific surface area, resulting in a final decrease in adsorption capacity. This law reflects that low doping amount of Ce02can promote the improvement of CO2capture performance of the sorbent in the short term through interface activation and pore regeneration, but long-term stability of the sorbent still needs to be maintained by further inhibiting high-temperature sintering.

[0060] Further, with the increase of CeO2doping amount, the CO2 cyclic capture performance of the adsorbent is obviously improved, wherein the carbonation conversion rate of Ca85Ce15 is maintained at about 83%, and the deactivation rate is only 2.1%, while the deactivation rate of Ca100 adsorbent is 19.21%, which shows that the ultrasonic pickling doped CeO2 can effectively improve the CO2 cyclic capture performance of the adsorbent. This is mainly because the ultrasonic pickling assisted doped CeO2 can form uniformly dispersed nano CeO2 particles, and can form an inert skeleton at the grain boundary, effectively spatially isolating the CaO grains at the micro level, reducing the grain boundary diffusion and grain migration rate, making it difficult for CaO particles to contact each other under high temperature cycling, significantly inhibiting sintering, reducing the specific surface area loss, and maintaining the pore channel; at the same time, the CeO2 of Ce 4+ / Ce 3+ The reversible valence change and rich oxygen vacancy characteristics can further enrich the pore channel of the adsorbent, which is beneficial to the diffusion of CO2 into the interior and reaction with active CaO.

[0061] The initial cycle reaction rate graph of the adsorbent under different doping amounts is shown in Figure 7 It can be found that the desorption rate of Ca95Ce5, which has the worst initial cycle CO2 capture performance, is the highest among the four adsorbents. This further shows that the carbonate phase formed on the surface of the adsorbent after carbonation reaction has poor stability, and the combination of CO2 and CaO is significantly weakened. This result has the same kinetic nature as the low carbonation conversion rate in the adsorption process, that is, CeO2 is distributed in the pore channel of the adsorbent, which reduces the interaction between CaO and CO2, making it more difficult for carbonation reaction to occur, and the rapid desorption behavior of Ca95Ce5 further verifies the adverse effect of low CeO2 doping amount on the initial capture performance.

[0062] The above examples are only used to illustrate the technical solutions of the present application and not to limit it, although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present application.

Claims

1. A method for preparing a calcium-based CO2 adsorbent, characterized in that, Includes the following steps: After dissolving the metal oxide precursor in an acidic solution, calcium-based alkaline industrial solid waste is added. The resulting mixture is then acidified and modified under ultrasonic conditions. Once the ultrasonic treatment is completed, the calcium-based CO2 adsorbent is obtained. The metal oxide precursor is at least one of cerium nitrate, manganese nitrate, magnesium nitrate, and zirconium nitrate.

2. The preparation method according to claim 1, characterized in that, The calcium-based alkaline industrial solid waste is carbide slag, and the mass percentage of the metal oxide in the calcium-based CO2 adsorbent is 5-30%.

3. The preparation method according to claim 1, characterized in that, The acidic solution is an acetic acid solution with a mass percentage of 10-20%.

4. The preparation method according to claim 1, characterized in that, The conditions for the ultrasonic process are as follows: power of 200W, frequency of 40kHz, and temperature of 60℃.

5. A calcium-based CO2 adsorbent prepared by the method according to any one of claims 1-4, characterized in that, The calcium-based CO2 adsorbent contains 70-95% CaO by mass.

6. The calcium-based CO2 adsorbent according to claim 5, characterized in that, The specific surface area of ​​the calcium-based CO2 adsorbent is 9-13 m². 2 / g, total pore volume is 0.04-0.05cm³ 3 / g, with an average pore size of 17-20nm.

7. The application of a calcium-based CO2 adsorbent prepared by any one of claims 1-4 or the calcium-based CO2 adsorbent of claim 6 in CO2 capture.

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