A solid acid nanosheet catalyst for desorbing CO2-rich absorbent and its preparation method

Abstract

The present invention discloses a solid acid nanosheet catalyst for catalyzing the desorption of CO2-rich absorption liquid and a preparation method thereof. Since the straight channels of MFI zeolite are parallel to the b-axis, faster diffusion rates can be observed in this direction. When the nanocrystal size is below 50 nm, the influence of diffusion limitation is significantly alleviated. Therefore, reducing the b-axis thickness of MFI zeolite is an effective strategy to reduce diffusion limitation. The present invention designs nanosheet HZSM-5 zeolite with a short b-axis thickness < 50 nm for the desorption of CO2-rich absorption liquid, thereby reducing the diffusion limitation of CO2 desorption, enhancing the desorption mass transfer rate, reducing the regeneration energy consumption of CO2-rich absorption liquid, and reducing the cost of capturing CO2.

Description

Technical Field

[0001] The present invention belongs to the field of CO2 capture, and particularly relates to a catalyst for catalyzing the desorption of CO2-rich absorption liquid. Background Art

[0002] China is the world's largest energy consumer. The increasing energy demand has led to the extensive use of fossil fuels in power plants, resulting in an increase in carbon dioxide (CO2) emissions, which has greatly damaged the atmospheric environment. The absorption of CO2 by aqueous monoethanolamine (MEA) solvent plays a key role in post-combustion CO2 capture. However, in the traditional MEA technology, due to the endothermic reaction of carbamate decomposition, CO2 desorption often occurs at high temperatures (110 - 140 °C). This desorption process accounts for more than 70% of the total heat loss of the CO2 capture device, and the high energy consumption hinders the large-scale industrial application of CO2 capture technology.

[0003] Zeolites are an important class of porous inorganic crystalline materials, mainly including silicate (germanate) (such as ZSM-5), phosphate (arsenate) (such as AIPO4-5), or silico-phosphate (such as SAPO-34). Due to their rich framework topologies and elemental compositions, zeolite molecular sieves have been widely used in ion exchange, adsorption separation, and catalysis since their synthesis. In the past decade, although remarkable progress has been made in the catalytic desorption of CO2 by zeolites, the mass transfer limitation caused by the existence of long microporous channels in three-dimensional (3D) zeolite materials remains an unsolved problem, which not only leads to low utilization efficiency of the active volume of zeolites but also limits the transport efficiency in separation and catalytic processes. The HZSM-5 zeolite (MFI framework) catalyst has high acidity, excellent Bronsted acid sites (BAS) and Lewis acid sites (LAS). Researchers have used it to accelerate the proton transfer rate of the CO2-rich liquid desorption process and reduce the desorption reaction heat of carbamate (AmineCOO-), so as to achieve the purpose of reducing the energy demand in the CO2-rich liquid desorption process. Shi et al. (Int. J Greenh. Gas Con., 2014, 26: 39 - 50.) first proposed using the solid acid catalyst HZSM-5 to promote CO2 desorption and reduce the energy consumption of solvent regeneration. Compared with the case without adding a catalyst, adding HZSM-5 can reduce the energy consumption by 35%. Patent CN 111715274 discloses a preparation method and application of a heterogeneous catalyst for desorbing CO2 in a solution. The catalyst SO4 2- / Metal oxide-HZSM-5 is used for the desorption of CO₂-rich amine solution. Compared with the case without a catalyst, the desorption rate is increased by 35-45%, and it can be recycled more than 4 times. Although HZSM-5 zeolite has excellent catalytic performance, it has two intersecting 10-membered ring channels, and its micropore size is in the range of 0.5-0.6 nm. The existence of micropores limits the diffusion and mass transfer of CO₂. Therefore, the limitation brought by the existence of long micropore channels in three-dimensional (3D) zeolite materials remains an issue to be solved, which not only leads to low utilization efficiency of the active volume of zeolite, but also limits the transport efficiency in the molecular sieve. This negative impact is particularly prominent for diffusion-limited reactions. The quite long micropores in bulk zeolite seriously hinder the diffusion of molecules, resulting in pore blockage and catalyst deactivation. Currently, all reports on using solid acid to catalyze CO₂ desorption adopt bulk zeolite, which greatly affects the diffusion rate and desorption efficiency of CO₂ desorption. Summary of the Invention

[0004] Aiming at the deficiencies of the prior art, the purpose of the present invention is to provide a solid acid nanosheet catalyst for catalyzing the desorption of CO₂-absorbed rich liquid and its preparation method. By designing HZSM-5 zeolite with a short b-axis thickness nanosheet for the desorption of CO₂-absorbed rich liquid, the diffusion limitation of CO₂ desorption is reduced, the desorption mass transfer rate is increased, thereby reducing the regeneration energy consumption of CO₂-absorbed rich liquid and the cost of capturing CO₂.

[0005] Since the straight channels of MFI zeolite are parallel to the b-axis, faster diffusion rates can be observed in this direction. When the nanocrystal size is below 50 nm, the influence of diffusion limitation is significantly alleviated. Therefore, reducing the b-axis thickness of MFI zeolite is an effective strategy to reduce diffusion limitation. The present invention designs and synthesizes MFI zeolite with a short diffusion length along the b-axis, which can reduce the influence of diffusion limitation in catalyzing CO₂ desorption and improve the desorption efficiency.

[0006] The solid acid nanosheet catalyst (HZSM-5 zeolite) for catalyzing the desorption of CO₂-absorbed rich liquid provided by the present invention is a nanosheet of HZSM-5 zeolite (MFI zeolite), and its b-axis thickness < 150 nm, preferably 20 nm < b-axis thickness < 150 nm, more preferably 20 nm < b-axis thickness < 50 nm.

[0007] The preparation method of the solid acid nanosheet (HZSM-5 nanosheet) catalyst for catalyzing the desorption of CO₂-absorbed rich liquid provided by the present invention includes the following steps:

[0008] (1) Synthesis of nanocrystal seed suspension

[0009] The nanocrystal seed suspension is prepared under hydrothermal treatment. 10 - 60 parts by mass of tetraethyl orthosilicate (TEOS) and 50 - 80 parts by mass of tetrapropylammonium hydroxide are mixed and stirred at 20 - 40 °C for 4 - 6 hours to obtain a hydrolyzed clear solution; the obtained solution is heated to 40 - 60 °C to remove the ethanol generated by the hydrolysis of TEOS; then the solution is transferred to a stainless-steel autoclave with a polytetrafluoroethylene liner and hydrothermally treated at 50 - 90 °C under static conditions for 24 - 72 hours to obtain a nanocrystal seed suspension with a size of 20 nm.

[0010] (2) Synthesis of HZSM-5 nanosheets

[0011] The silicon source, organic base, deionized water, and nanocrystal seed suspension are mixed to form solution A; the aluminum source and NH4F are respectively dissolved in deionized water to form solution B and solution C; after stirring solution A at 35 °C for 4 - 6 hours, solution B and solution C are successively added dropwise to obtain a mixed solution; the mixed solution is vigorously stirred for 1 - 2 hours to obtain a precursor gel; the obtained gel is transferred to a stainless-steel autoclave with a polytetrafluoroethylene liner and crystallized at 170 °C for 1 day, then the solid product is centrifuged 2 - 3 times, rinsed with deionized water until neutral, dried at 80 - 100 °C for 12 - 24 hours, and then calcined in air at 500 - 600 °C for 4 - 6 hours to obtain HZSM-5 nanosheets.

[0012] Among them, the molar ratio of the total amount of the silicon source, aluminum source, organic base, NH4F, and deionized water used is calculated as SiO2:Al2O3:organic base:NH4F:H2O = 1:(0.001 - 0.1):(0.01 - 1.0):(0.1 - 1.0):(50 - 200), that is, the amount of the silicon source is calculated based on the amount of SiO2 in it for the proportion calculation, the amount of the aluminum source is calculated based on the amount of aluminum oxide Al2O3 in it for the proportion calculation, and the deionized water is the total amount of deionized water used in this step. The addition amount of the nanocrystal seed suspension accounts for 0.1 - 100% of the mass of SiO2 in the silicon source.

[0013] In the above method, further, the molar ratio of the total amount of the silicon source, aluminum source, organic base, NH4F, and deionized water used is preferably SiO2:Al2O3:organic base:NH4F:H2O = 1:0.04:0.14:0.8:160.

[0014] In the above method, further, the silicon source is at least one of tetraethyl orthosilicate and silica sol; the organic base is at least one of tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, and tetrapropylammonium bromide; the aluminum source is at least one of aluminum nitrate, aluminum trichloride, and aluminum isopropoxide.

[0015] The present invention also provides an application of the above solid acid nanosheets in the desorption of the rich solution of CO2 absorption. The rich solution of CO2 absorption refers to the solution obtained by absorbing CO2 through an aqueous solution of an alcoholamine chemical absorbent in CO2 capture.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] The present invention designs nanosheet HZSM-5 zeolite with a short b-axis thickness for the desorption of the rich solution of CO2 absorption, reduces the diffusion limitation of CO2 desorption, improves the desorption mass transfer rate, and realizes low-energy catalytic desorption of CO2. Description of the Drawings

[0018] Figure 1 SEM images (including b-axis thickness distribution diagrams) of nanosheets with different b-axis thicknesses prepared for the examples: (a) ZN-1 130 nm; (b) ZN-2 40 nm; (c) ZN-3 50 nm; (d) ZN-4 85 nm; (e) ZN-5 130 nm; (f) SEM image (including b-axis thickness distribution diagram) of NK-Z5 of Comparative Example 2;

[0019] Figure 2 XRD patterns of zeolites of nanosheets with different b-axis thicknesses;

[0020] Figure 3 N2 adsorption-desorption isotherm curves of zeolites of nanosheets with different b-axis thicknesses prepared for the examples;

[0021] Figure 4 NH3-TPD of zeolites of nanosheets with different b-axis thicknesses prepared for the examples;

[0022] Figure 5 Py-IR of zeolites of nanosheets with different b-axis thicknesses prepared for the examples. Detailed Embodiments

[0023] The present invention will be further described below through examples. It is necessary to point out that the following examples are only used to further illustrate the present invention and cannot be understood as limiting the protection scope of the present invention. Those skilled in the art make some non-essential improvements and adjustments to the present invention according to the above-mentioned invention content and conduct specific implementation, which still belongs to the protection scope of the invention.

[0024] In the following examples, the prepared HZSM-5 nanosheets are denoted as ZN-y (y is the number of different samples).

[0025] Example 1

[0026] (1) Synthesis of nanocrystal seed suspension:

[0027] The nanocrystal seed suspension was prepared under hydrothermal treatment. 30 g of tetraethyl orthosilicate (TEOS) was mixed with 50 g of tetrapropylammonium hydroxide and stirred at 35 °C for 4 hours to obtain a clear hydrolyzed solution; the solution was heated to 45 °C to remove the ethanol produced by the hydrolysis of TEOS, and then transferred to a stainless-steel autoclave with a polytetrafluoroethylene liner, and hydrothermally treated at 70 °C under static conditions for 72 hours to obtain the nanocrystal seed suspension.

[0028] (2) Synthesis of HZSM-5 nanosheets

[0029] TEOS, tetraethylammonium hydroxide and the nanocrystal seed suspension were dissolved in a certain amount of deionized water to form solution A. Aluminum nitrate and NH4F were respectively dissolved in deionized water to form solution B and C. After stirring solution A at 35 °C for 6 hours, solution B and C were successively added dropwise to obtain a mixed solution. The mixed solution was continuously stirred vigorously for 2 hours to obtain a precursor gel, and then transferred to a stainless-steel autoclave with a polytetrafluoroethylene liner. After crystallization at 170 °C for 1 day, the solid product was centrifuged 3 times, rinsed with deionized water until neutral, and dried at 80 °C for 12 hours. The dried solid was calcined in air at 550 °C for 6 hours to obtain HZSM-5 nanosheets, labeled as ZN-1. Among them, the molar ratio of each part was 1SiO2:0.04Al2O3:0.2 organic base:0.8NH4F:150H2O; the addition amount of the nanocrystal seed suspension accounted for 50% of the mass of SiO2.

[0030] Experimental procedure

[0031] Using a self-made CO2 absorption-desorption integrated device in the laboratory, the performance of the HZSM-5 nanosheets prepared in Example 1 for catalyzing CO2 desorption was evaluated. The absorption was carried out by using a mass flowmeter to simulate the flue gas composition (15% CO2 - 85% N2); the desorbed CO2 was diluted with an additional N2 flow, and the concentration of the mixed stream was measured by an infrared gas analyzer.

[0032] 1. Absorption experiment

[0033] 500 ml of an aqueous solution of ethanolamine with a mass fraction of 30% was used to simulate low-concentration CO2 flue gas with a N2 / CO2 mixed gas (85 Vol.% / 15 Vol.%), and an absorption-rich liquid with a CO2 loading of 0.52 mol CO2 / mol MEA was obtained.

[0034] The CO2 absorption rate and CO2 loading of the organic alkanolamine solution were calculated according to equations (1) and (2).

[0035]

[0036] where υ CO2is the CO2 absorption rate of the solution, ml / min; is the N2 inlet rate, 100 mL / min; a is the CO2 concentration percentage at the outlet; is the volume of CO2 absorbed by the solution within time t, mL; t is the time, min.

[0037] 2. Desorption experiment

[0038] Add 0.52 mol CO2 / mol MEA absorption-rich solution into the reaction flask, and add the catalysts described in the comparative examples and examples respectively; the blank is thermal desorption without adding a catalyst, and the addition amount of the catalyst is 0.5 - 2%. The desorption temperature is 80 - 100 °C, and the desorption time is 60 minutes.

[0039] Use an infrared gas analyzer to measure the CO2 concentration during desorption, and calculate the desorption rate and desorption amount of CO2 catalyzed by the catalyst using equations (3) and (4).

[0040]

[0041] In the formula, is the amount of CO2 desorbed by the solution within time t, mmol; V des is the CO2 desorption rate of the solution, mmol / s; χ is the CO2 concentration percentage at the desorption outlet.

[0042] 3. Calculation of CO2 desorption energy consumption

[0043] The evaluation parameter of the CO2 desorption performance catalyzed by the catalyst is the desorption energy consumption H (kJ / mol) per mole of CO2, which is defined as the ratio of the energy input rate to the CO2 desorption rate, and is calculated by the following formula (5):

[0044]

[0045] Here, E refers to the electricity consumption recorded by the electricity meter for CO2 desorption within a certain time, with the unit of kW·h, which needs to be converted to kJ when used.

[0046] Since the CO2 desorption energy consumption calculated by this method is only a relative value, in order to better evaluate the CO2 desorption performance catalyzed by the catalyst, this project proposes and defines a parameter of relative desorption energy consumption RH (%), with the desorption energy consumption of the blank alkanolamine solution for 90 min regeneration as the benchmark (H b , kJ / mol), and its RH is 100%, then the RH of the catalytic CO2 desorption process is the ratio of the desorption energy consumption H i (kJ / mol) of catalytic CO2 desorption for 90 min to H b , and is calculated by the following formula (6):

[0047]

[0048] Example 2

[0049] (1) The synthesis method of the nanocrystal seed suspension is the same as that in Example 1.

[0050] (2) Synthesis of HZSM-5 nanosheets:

[0051] Tetraethyl orthosilicate, tetrapropylammonium hydroxide and the nanocrystal seed suspension were dissolved in a certain amount of deionized water to prepare solution A. Aluminum nitrate and NH4F were respectively dissolved in deionized water to prepare solutions B and C. After stirring solution A at 35 °C for 6 hours, solutions B and C were successively added dropwise to obtain a mixed solution. The mixed solution was continuously stirred vigorously for 2 hours to obtain a precursor gel, and then transferred to a stainless steel autoclave with a polytetrafluoroethylene liner. After crystallization at 170 °C for 1 day, the solid product was centrifuged 3 times, rinsed with deionized water until neutral, and dried at 80 °C for 12 hours. Then, the dried solid was calcined in air at 550 °C for 6 hours to obtain HZSM-5 nanosheets, labeled as ZN-2. Among them, the molar ratio of the silicon source, aluminum source, organic base, NH4F to water is 1SiO2:0.04Al2O3:0.2 organic base:0.8NH4F:150H2O; the addition amount of the nanocrystal seed suspension accounts for 20% of the mass of SiO2.

[0052] The absorption and desorption experimental conditions and the energy consumption calculation method are the same as those in Example 1.

[0053] Example 3

[0054] (1) The synthesis method of the nanocrystal seed suspension is the same as that in Example 1.

[0055] (2) Synthesis of HZSM-5 nanosheets:

[0056] Tetraethyl orthosilicate, tetrapropylammonium bromide and the nanocrystals were dissolved in a certain amount of deionized water to prepare solution A. Aluminum nitrate and NH4F were respectively dissolved in deionized water to prepare solutions B and C. After stirring solution A at 35 °C for 6 hours, solutions B and C were successively added dropwise to obtain a mixed solution. The mixed solution was continuously stirred vigorously for 2 hours to obtain a precursor gel, and then transferred to a stainless steel autoclave with a polytetrafluoroethylene liner. After crystallization at 170 °C for 1 day, the solid product was centrifuged 3 times, rinsed with deionized water until neutral, and dried at 80 °C for 12 hours. Then, the dried solid was calcined in air at 550 °C for 6 hours to obtain HZSM-5 nanosheets, labeled as ZN-3. Among them, the molar ratio of each part is 1SiO2:0.04Al2O3:0.2 organic base:0.8NH4F:150H2O; the addition amount of the nanocrystal seed suspension accounts for 5% of the mass of SiO2.

[0057] The absorption and desorption experimental conditions and the energy consumption calculation method are the same as those in Example 1.

[0058] Example 4

[0059] (1) The synthesis method of the nanocrystal seed suspension is the same as that in Example 1.

[0060] (2) Synthesis of HZSM-5 nanosheets:

[0061] Tetraethyl orthosilicate, tetrabutylammonium hydroxide and nanocrystal seeds were dissolved in a certain amount of deionized water to form Solution A. Aluminum nitrate and NH4F were respectively dissolved in deionized water to form Solution B and Solution C. After stirring Solution A at 35 °C for 6 hours, Solutions B and C were successively added dropwise to obtain a mixed solution. The mixed solution was continuously stirred vigorously for 2 hours to obtain a precursor gel, which was then transferred to a stainless-steel autoclave with a polytetrafluoroethylene lining and crystallized at 170 °C for 1 day. The solid product was centrifuged 3 times, rinsed with deionized water until neutral, and dried overnight at 80 °C. Then, the dried solid was calcined in air at 550 °C for 6 hours to obtain HZSM-5 nanosheets, labeled as ZN-4. Among them, the molar ratio of each part is 1SiO2:0.04Al2O3:0.2 organic base:0.8NH4F:150H2O; the addition amount of the nanocrystal seed suspension accounts for 1% of the mass of SiO2.

[0062] The synthesis method of the nanocrystal seed suspension is the same as that in Example 1.

[0063] The absorption and desorption experimental conditions and the energy consumption calculation method are the same as those in Example 1.

[0064] Example 5

[0065] (1) The synthesis method of the nanocrystal seed suspension is the same as that in Example 1.

[0066] (2) Synthesis of HZSM-5 nanosheets:

[0067] Tetraethyl orthosilicate, tetraethylammonium hydroxide and nanocrystalline seeds were dissolved in a certain amount of deionized water to prepare solution A. Aluminum nitrate and NH4F were separately dissolved in deionized water to prepare solutions B and C. After stirring solution A at 35 °C for 6 hours, solutions B and C were successively added dropwise to obtain a mixed solution. The mixed solution was continuously stirred vigorously for 2 hours to obtain a precursor gel, which was then transferred to a stainless-steel autoclave with a polytetrafluoroethylene lining and crystallized at 170 °C for 1 day. The solid product was centrifuged several times, rinsed with deionized water until neutral, and dried at 80 °C overnight. Then, the dried solid was calcined in air at 550 °C for 6 hours to obtain HZSM-5 nanosheets, denoted as ZN-5. Among them, the molar ratio of each part was 1SiO2:0.04Al2O3:0.2 organic base:0.8NH4F:150H2O; the addition amount of the nanocrystalline seed suspension accounted for 0.1% of the mass of SiO2.

[0068] The absorption and desorption experimental conditions and the energy consumption calculation method were the same as those in Example 1.

[0069] Comparative Example 1

[0070] The absorption and desorption experimental conditions and the energy consumption calculation method were the same as those in Example 1, without adding a catalyst, denoted as blank.

[0071] Comparative Example 2

[0072] The absorption and desorption experimental conditions and the energy consumption calculation method were the same as those in Example 1. Commercially available HZSM-5 zeolite from Nankai University (conventional b-axis thickness 80 - 800 nm) was purchased for comparison, denoted as NK-Z5.

[0073] Nanosheet zeolites with different b-axis thicknesses were synthesized by adjusting the amount of nanocrystalline seeds. SEM images ( Figure 1 ) confirmed the successful synthesis of the nanosheets. The average b-axis thicknesses were (a) ZN-1 30 nm; (b) ZN-2 40 nm; (c) ZN-3 50 nm; (d) ZN-4 90 nm; (e) ZN-5 130 nm. Further, from Figure 2 It can be seen that diffraction peaks appeared at 7.9°, 8.8°, 23.1°, 23.9° and 24.3° for the synthesized nanosheet zeolite samples with different b-axis thicknesses, showing the typical MFI topological structure of H-ZSM-5, indicating that adjusting the nanosheet thickness did not change its structural characteristics.

[0074] Figure 3 The N2 adsorption - desorption isotherm curves of nanosheet zeolites with different b-axis thicknesses are shown. At a relative pressure (P / P0) of 0.01 - 0.9, obvious type I isotherms could be observed for all samples, indicating that all HZSM-5 nanosheets had a typical microporous structure. With the increase of nanocrystalline seeds (Table 1), the specific surface area (420 → 482 m2 g -1 ) and the mesoporous volume (0.057 → 0.229 cm 3 g -1 ) increased significantly, and among the samples, the ZN-1 sample had the highest specific surface area and mesoporous volume, which was due to the stacking between very thin nanosheets, facilitating the improvement of the accessibility to acidic sites and the carbon deposition capacity of the catalyst.

[0075] As can be seen from Table 2, the ZN-1 sample with a b-axis thickness of 30 nm had the most excellent catalytic desorption performance. Compared with traditional thermal desorption (blank), the desorption energy consumption was reduced by 35.4%. There were mainly three reasons for the reduction of desorption energy consumption. First, among the five nanosheet zeolites, the ZN-1 sample had the smallest b-axis thickness (30 nm). The straight channels of MFI zeolite were parallel to the b-axis, and the smaller the b-axis thickness, the faster the desorption diffusion rate. Second, by quantifying the NH3-TPD of the five nanosheet zeolites, it was found that while the b-axis thickness was shortened, the total acid amount of the zeolite gradually increased ( Figure 4 ), and the ZN-1 sample had the highest total acid amount. Although the total acid amount of NK-Z5 in Comparative Example 2 was higher than that of the ZN-1 sample, due to its relatively wide b-axis thickness (700 nm, Figure 1 f), it affected its desorption diffusion rate and thus the desorption rate. Third, further analyzing the changes in the ratio of Brønsted acid to Lewis acid of the five nanosheet zeolites by pyridine infrared, the results are shown in Table 1, Figure 5 . It can be seen that the increased acid amount due to the shortening of the b-axis thickness was mainly the increase in the content of Brønsted acid, which could enhance the cleavage of carbamate (Amine - COO - ) during the CO2 desorption process and improve the desorption rate.

[0076] Table 1 Structure and acid properties of nanosheet zeolites with different b-axis thicknesses

[0077]

[0078]

[0079] Note: The total acid amount was calculated from the NH3-TPD spectrum. B / L is the ratio of Brønsted acid to Lewis acid, obtained by pyridine infrared.

[0080] Table 2 Comparison of relative desorption energy consumption of the catalysts in the examples

[0081] Number Catalyst Relative desorption energy consumption RH(%) Energy consumption reduction(%) b-axis thickness(nm) Comparative Example 1 Blank 100 / / Comparative Example 2 NK-Z5 81.2 18.8 700 Example 1 ZN-1 64.6 35.4 30 Example 2 ZN-2 69.4 30.6 40 Example 3 ZN-3 70.7 29.3 50 Example 4 ZN-4 73.2 26.8 90 Example 5 ZN-5 74.5 25.5 130

[0082] Note: The b-axis thickness of the zeolite was obtained from the SEM image.

Claims

1. A solid acid nanosheet catalyst for desorbing rich liquid of CO2 absorption, characterized in that, The catalyst is HZSM-5 zeolite nanosheets with a b-axis thickness < 150 nm, and the catalyst is prepared by the following method: (1) Synthesis of nanocrystal seed suspension The nanocrystal seed suspension is prepared under hydrothermal treatment; 10-60 parts by mass of tetraethyl orthosilicate (TEOS) and 50-80 parts by mass of tetrapropylammonium hydroxide are mixed and stirred at 20-40 °C for 4-6 hours to obtain a hydrolyzed clear solution; The obtained solution is heated to 40-60 °C to remove the ethanol produced by the hydrolysis of TEOS; Then the solution is transferred to a stainless steel autoclave with a polytetrafluoroethylene lining and hydrothermally treated at 50-90 °C under static conditions for 24-72 hours to obtain a nanocrystal seed suspension with a size of 20 nm; (2) Synthesis of solid acid nanosheet HZSM-5 nanosheets The silicon source, organic base, deionized water and nanocrystal seed suspension are mixed to form solution A; the aluminum source and NH4F are respectively dissolved in deionized water to form solution B and solution C; After stirring solution A at 35 °C for 4-6 h, solution B and solution C are successively added dropwise to obtain a mixed solution; the mixed solution is vigorously stirred for 1-2 h to obtain a precursor gel; The obtained gel is transferred to a stainless steel autoclave with a polytetrafluoroethylene lining and crystallized at 170 °C for 1 day. Then the solid product is centrifuged 2-3 times, rinsed with deionized water until neutral, dried at 80-100 °C for 12-24 hours, and then calcined in air at 500-600 °C for 4-6 hours to obtain HZSM-5 nanosheets; Among them, the molar ratio of the total amount of the silicon source, aluminum source, organic base, NH4F, and deionized water used is calculated as SiO2:Al2O3:organic base:NH4F:H2O = 1:(0.001-0.1):(0.01-1.0):(0.1-1.0):(50-200), that is, the amount of the silicon source is calculated based on the participation ratio of SiO2, the amount of the aluminum source is calculated based on the participation ratio of aluminum oxide Al2O3 therein, and the deionized water is the total amount of deionized water used in this step.

2. The solid acid nanosheet catalyst for catalytic desorption of CO2-absorbed rich liquid according to claim 1, wherein Its b-axis thickness is 20 nm < b-axis thickness < 50 nm.

3. A preparation method of a solid acid nanosheet catalyst for catalyzing the desorption of CO2-rich absorption solution, characterized in that, It includes the following steps: (1) Synthesis of nanocrystal seed suspension The nanocrystal seed suspension is prepared under hydrothermal treatment; 10-60 parts by mass of tetraethyl orthosilicate (TEOS) and 50-80 parts by mass of tetrapropylammonium hydroxide are mixed and stirred at 20-40 °C for 4-6 hours to obtain a hydrolyzed clear solution; The obtained solution is heated to 40-60 °C to remove the ethanol produced by the hydrolysis of TEOS; Then the solution is transferred to a stainless steel autoclave with a polytetrafluoroethylene lining and hydrothermally treated at 50-90 °C under static conditions for 24-72 hours to obtain a nanocrystal seed suspension with a size of 20 nm; (2) Synthesis of solid acid nanosheet HZSM-5 nanosheets The silicon source, organic base, deionized water and nanocrystal seed suspension are mixed to form solution A; the aluminum source and NH4F are respectively dissolved in deionized water to form solution B and solution C; After stirring solution A at 35 °C for 4 - 6 h, solution B and C were added dropwise in sequence to obtain a mixed solution; the mixed solution was vigorously stirred for 1 - 2 h to obtain a precursor gel; The obtained gel was transferred to a stainless - steel autoclave with a polytetrafluoroethylene liner. After crystallization at 170 °C for 1 day, the solid product was centrifuged 2 - 3 times, rinsed with deionized water until neutral, dried at 80 - 100 °C for 12 - 24 h, and then calcined in air at 500 - 600 °C for 4 - 6 h to obtain HZSM - 5 nanosheets; Among them, the molar ratio of the total amount of silicon source, aluminum source, organic base, NH4F, and deionized water used is SiO2:Al2O3:organic base:NH4F:H2O = 1:(0.001 - 0.1):(0.01 - 1.0):(0.1 - 1.0):(50 - 200). That is, the amount of the silicon source is calculated based on the participation ratio of SiO2, the amount of the aluminum source is calculated based on the participation ratio of its aluminum oxide Al2O3, and the deionized water is the total amount of deionized water used in this step.

4. The method according to claim 3, wherein The addition amount of the nanocrystal seed suspension accounts for 0.1% - 100% of the mass of SiO2 in the silicon source.

5. The method according to claim 3, wherein The silicon source is at least one of tetraethyl orthosilicate and silica sol.

6. The method according to claim 3, characterized in that, The organic base is at least one of tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, and tetrapropylammonium bromide.

7. The method according to claim 3, characterized in that The aluminum source is at least one of aluminum nitrate, aluminum trichloride, and aluminum isopropoxide.

8. Application of the solid acid nanosheet catalyst described in claim 1 in the desorption of CO2 - rich absorption liquid.

9. The application according to claim 8, wherein The CO2 - rich absorption liquid refers to the solution obtained by absorbing CO2 through an aqueous solution of an alkanolamine - based chemical absorbent in CO2 capture.

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