Synthesis method of 13X molecular sieve

Abstract

The present invention provides a 13X molecular sieve and a synthesis method thereof, and relates to the technical field of molecular sieve catalyst preparation, the synthesis method comprises: mixing a sodium aluminate solution, a sodium hydroxide solution and a sodium metasilicate nonahydrate solution, uniformly stirring, stirring for a first time at a first temperature, carrying out a hydrothermal reaction for a second time at a second temperature, and finally filtering, drying and calcining to obtain the 13X molecular sieve. The 13X molecular sieve is obtained. The synthesized 13X molecular sieve has good CO2 adsorption performance, and the CO2 adsorption capacity can reach 6.23 mmol / g. The selectivity ratio of carbon dioxide to nitrogen reaches 57, and the obvious selectivity on carbon dioxide is superior to that of nitrogen, so that the catalyst has good selectivity. In an adsorption-regeneration cycle test, a sample shows stable adsorption-regeneration performance, the adsorption capacity is not obviously reduced, and the sample has good stability under static and dynamic adsorption conditions.

Description

Technical Field

[0001] This invention belongs to the field of molecular sieve catalyst preparation technology, specifically relating to a method for synthesizing 13X molecular sieve. Background Technology

[0002] Against the backdrop of global climate change, carbon capture, utilization, and storage (CCUS) technology has become a pathway to achieving carbon neutrality. However, its technological cost is a significant factor affecting industrial applications. Accelerating the development of new technologies with low energy consumption, high performance, and large-scale application is an important means to reduce the cost of carbon dioxide capture.

[0003] 13X zeolite, as a promising solid adsorbent, has attracted attention due to its low energy consumption, high stability, and environmental friendliness compared to traditional liquid adsorption methods. However, compared with other types of solid adsorbents, the adsorption capacity and selectivity of 13X molecular sieves still have room for improvement. Studies have shown that the differences in CO2 adsorption performance (including adsorption capacity and selectivity) of 13X molecular sieves mainly stem from significant differences in their pore structure (ultra-micropore / micropore / mesopore distribution) and specific surface area, which are significantly affected by synthesis methods and process conditions (such as raw materials, silica-alumina ratio, temperature, crystal size, etc.). Research indicates that differences in synthesis methods and process conditions can significantly modulate the specific surface area and pore structure of 13X molecular sieves, affecting their adsorption performance and selectivity. Summary of the Invention

[0004] In view of this, this application provides a method for synthesizing 13X molecular sieves to prepare 13X molecular sieves with excellent CO2 adsorption performance.

[0005] The technical solution adopted by this invention to solve its technical problem is:

[0006] A method for synthesizing 13X molecular sieve includes the following steps:

[0007] S10. Mix sodium aluminate solution, sodium hydroxide solution, and sodium metasilicate nonahydrate solution and stir until homogeneous to obtain a reaction solution;

[0008] S20. The reaction solution is stirred at the reaction temperature for a first time to obtain a reaction gel; wherein the reaction temperature is 25°C to 60°C to allow the crystals to grow in an orderly manner.

[0009] S30. The reaction gel is subjected to hydrothermal reaction at a hydrothermal reaction temperature for a second time, then filtered and dried to obtain the reactant; wherein the hydrothermal reaction temperature is 80°C to 120°C to adjust the nucleation rate of the zeolite framework, crystal growth orientation and selective development of crystal faces.

[0010] S40. The reactants are calcined in an inert gas atmosphere at 400°C to 800°C for a third time to remove residual impurities and adjust the pore structure to obtain 13X molecular sieve.

[0011] Preferably, in step S10, sodium aluminate solution and sodium metasilicate nonahydrate solution are added dropwise to sodium hydroxide solution under stirring conditions, with a stirring rate of 500~700 r / min.

[0012] Preferably, the mass ratio of sodium aluminate, sodium hydroxide and sodium metasilicate nonahydrate is 1:1-5:5-10.

[0013] Preferably, in step S20, the reaction temperature is 25°C to 45°C, and in step S30, the hydrothermal reaction temperature is 80°C to 100°C.

[0014] Preferably, the calcination temperature is 400°C to 600°C.

[0015] Preferably, the second duration is 8 to 12 hours, and the third duration is 2 to 6 hours.

[0016] Preferably, the first duration is 20 hours to 30 hours.

[0017] Preferably, the concentration of the sodium aluminate solution is 1.22 mol / L, the concentration of the sodium hydroxide solution is 2.5 mol / L, and the concentration of the sodium metasilicate nonahydrate solution is 1.34 mol / L.

[0018] The 13X molecular sieve prepared by the above-described synthesis method has micropores of 0.6-1.4 nm accounting for more than 70% of the total pore volume.

[0019] The molecular sieve prepared by the above-described synthesis method for 13X molecular sieve has a CO2 adsorption capacity of 6.23 mmol / g or higher and a carbon dioxide / nitrogen selectivity ratio of 57 or higher.

[0020] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0021] The method for synthesizing 13X molecular sieve disclosed in this application involves mixing sodium aluminate solution, sodium hydroxide solution, and sodium metasilicate nonahydrate solution and stirring until homogeneous to form a uniform gel, thus obtaining a reaction solution. The reaction solution is then stirred at 25°C to 60°C for a first time to obtain another reaction solution. This reaction solution is then subjected to a hydrothermal reaction at 80°C to 120°C for a second time, followed by filtration and drying to obtain a reactant. The reactant is then calcined in an inert gas atmosphere at 400°C to 800°C for a third time to obtain the 13X molecular sieve. Therefore, by adjusting the gel formation temperature beforehand to promote orderly crystal growth and ensure a complete crystal structure, and then adjusting the crystallization temperature to adjust the nucleation rate of the zeolite framework, crystal growth orientation, and selective development of crystal faces, the formation of the zeolite framework and morphology is controlled. Finally, adjusting the calcination temperature removes residual impurities from the synthesized zeolite and adjusts the pore structure to obtain a 13X molecular sieve with excellent crystallinity and phase purity, and where all zeolite particles exhibit an octahedral structure.

[0022] Simultaneously, by controlling the gel formation temperature, crystallization temperature, and calcination temperature, the effective micropore surface area and effective micropore volume are precisely controlled, thereby adjusting the CO2 adsorption capacity through the synergistic effect of micropore filling and effective adsorption sites; therefore, the effective micropore surface area of ​​the 13X molecular sieve prepared by this invention is 673.48 m². 2 / g, with an effective micropore volume of 0.257cm³. 3 / g, with a good ratio of effective micropore specific surface area (Smicro) to micropore volume (Vmicro), sufficient effective adsorption active sites, and excellent CO2 adsorption performance of 13X molecular sieve.

[0023] The 13X molecular sieve synthesized in this application exhibits carbon dioxide / nitrogen selectivity ratios of 57 and 149 at 0℃ and 25℃, respectively, with significantly better selectivity for carbon dioxide than for nitrogen, indicating its excellent selectivity. In adsorption-regeneration cycle tests, the sample demonstrated stable adsorption-regeneration performance, with no significant decrease in adsorption capacity, and good stability under both static and dynamic adsorption conditions. Attached Figure Description

[0024] Figure 1 XRD patterns of 13X molecular sieves prepared under different synthetic conditions, among which Figure 1 (a) represents different hydrothermal reaction temperatures; Figure 1 (b) represents different hydrothermal reaction times; Figure 1 (c) represents different reaction temperatures; Figure 1 (d) represents different calcination temperatures.

[0025] Figure 2Scanning electron microscope (SEM) images of 13X molecular sieves prepared under different synthetic conditions, where (a) H-80, (b) H-100, (c) H-120, (d) H-8, (e) H-14, (f) H-16, (g) R-45, (h) R-60, (i) C-400, (j) C-600, (k) C-700, and (l) C-800.

[0026] Figure 3 The figures show nitrogen adsorption-desorption isotherms for 13X molecular sieves prepared under different synthesis conditions. Figure 3 (a) represents different hydrothermal reaction temperatures; Figure 3 (b) represents different hydrothermal reaction times; Figure 3 (c) represents different reaction temperatures; Figure 3 (d) represents different calcination temperatures.

[0027] Figure 4 Pore ​​size diagrams of 13X molecular sieves prepared under different synthesis conditions.

[0028] Figure 5 The effects of pressure and temperature on carbon dioxide adsorption capacity, among which Figure 5 (a) CO2 adsorption capacity of 13X molecular sieves synthesized at different hydrothermal reaction temperatures at 0℃; Figure 5 (b) CO2 adsorption capacity of 13X molecular sieves synthesized at 0℃ for different hydrothermal reaction times; Figure 5 (c) CO2 adsorption capacity of 13X molecular sieves synthesized at different reaction temperatures at 0℃; Figure 5 (d) represents the CO2 adsorption capacity of 13X molecular sieves synthesized at different calcination temperatures at 0℃; Figure 5 (e) CO2 adsorption capacity of 13X molecular sieves synthesized at different hydrothermal reaction temperatures at room temperature; Figure 5 (f) represents the CO2 adsorption capacity of 13X molecular sieves synthesized at different hydrothermal reaction times at room temperature; Figure 5 (g) represents the CO2 adsorption capacity of 13X molecular sieves synthesized at different reaction temperatures at room temperature; Figure 5 (h) represents the CO2 adsorption capacity of 13X molecular sieves synthesized at different calcination temperatures at room temperature.

[0029] Figure 6 Carbon dioxide for 13X molecular sieve ( Figure 6 a and Figure 6 b) and nitrogen ( Figure 6 c and Figure 6 d) Adsorption-desorption isotherm curves and ( Figure 6 e) IAST selectivity curve of 13X molecular sieve for a binary gas mixture (carbon dioxide / nitrogen = 15:85) at 298 K.

[0030] Figure 7 The carbon dioxide cyclic adsorption capacity of sample 5 (labeled H-100) in this application embodiment is shown in the physicochemical adsorption analyzer (a) and thermogravimetric analyzer (b).

[0031] Figure 8 Screening chart for the separation performance of H-100 and C-13X for CO2 / N2 mixtures.

[0032] Figure 9 The separation performance of H-100 and C-13X for CO2 / N2 mixtures. Detailed Implementation

[0033] The technical solutions and effects of the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0034] This application provides a method for synthesizing 13X molecular sieves, comprising the following steps:

[0035] S10. Mix sodium aluminate solution, sodium hydroxide solution, and sodium metasilicate nonahydrate solution and stir until homogeneous to obtain a reaction solution;

[0036] S20. The reaction solution is stirred at the reaction temperature for a first time to obtain a reaction gel; wherein the reaction temperature is 25°C to 60°C.

[0037] S30. The reaction gel is subjected to hydrothermal reaction at a hydrothermal reaction temperature for a second time, then filtered and dried to obtain the reactant; wherein the hydrothermal reaction temperature is 80°C to 120°C;

[0038] S40. The reactants are calcined in an inert gas atmosphere at 400°C to 800°C for a third time to obtain 13X molecular sieve.

[0039] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0040] The method for synthesizing 13X molecular sieve disclosed in this application involves mixing sodium aluminate solution, sodium hydroxide solution, and sodium metasilicate nonahydrate solution and stirring until homogeneous to form a uniform gel, thus obtaining a reaction solution. The reaction solution is then stirred at 25°C to 60°C for a first time to obtain another reaction solution. This reaction solution is then subjected to a hydrothermal reaction at 80°C to 120°C for a second time, followed by filtration and drying to obtain a reactant. The reactant is then calcined in an inert gas atmosphere at 400°C to 800°C for a third time to obtain the 13X molecular sieve. Therefore, by adjusting the gel formation temperature beforehand to promote orderly crystal growth and ensure a complete crystal structure, and then adjusting the crystallization temperature to adjust the nucleation rate of the zeolite framework, crystal growth orientation, and selective development of crystal faces, the formation of the zeolite framework and morphology is controlled. Finally, adjusting the calcination temperature removes residual impurities from the synthesized zeolite and adjusts the pore structure to obtain a 13X molecular sieve with excellent crystallinity and phase purity, and where all zeolite particles exhibit an octahedral structure.

[0041] Simultaneously, by controlling the gel formation temperature, crystallization temperature, and calcination temperature, the effective micropore surface area and effective micropore volume are precisely controlled, thereby adjusting the CO2 adsorption capacity through the synergistic effect of micropore filling and effective adsorption sites; therefore, the effective micropore surface area of ​​the 13X molecular sieve prepared by this invention is 673.48 m². 2 / g, with an effective micropore volume of 0.257cm³. 3 / g, with a good ratio of effective micropore specific surface area (Smicro) to micropore volume (Vmicro), sufficient effective adsorption active sites, and excellent CO2 adsorption performance of 13X molecular sieve.

[0042] The 13X molecular sieve synthesized in this application exhibits carbon dioxide / nitrogen selectivity ratios of 57 and 149 at 0℃ and 25℃, respectively, with significantly better selectivity for carbon dioxide than for nitrogen, indicating its excellent selectivity. In adsorption-regeneration cycle tests, the sample demonstrated stable adsorption-regeneration performance, with no significant decrease in adsorption capacity, and good stability under both static and dynamic adsorption conditions.

[0043] In one embodiment, to avoid disordered microporous structures, in step S10, sodium aluminate solution and sodium metasilicate nonahydrate solution are added dropwise to sodium hydroxide solution under stirring conditions. The stirring rate is 500-700 r / min, and the mass ratio of sodium aluminate, sodium hydroxide, and sodium metasilicate nonahydrate is 1:1-5:5-10. Pure chemical reagents are used, and the material ratio of silicon to aluminum and the mass of solvent are strictly controlled. By using the dropwise addition process, the homogeneity and dispersibility of the reaction system can be precisely controlled. This homogeneous dispersion characteristic is not only conducive to optimizing the regularity of the microporous structure, but also to increasing the exposure of effective active sites, laying a key foundation for improving the separation performance of zeolite materials.

[0044] In one embodiment, the concentration of the sodium aluminate solution is 1.22 mol / L, the concentration of the sodium hydroxide solution is 2.5 mol / L, and the concentration of the sodium metasilicate nonahydrate solution is 1.34 mol / L. Therefore, based on the concentration of sodium hydroxide, the molecular sieve prepared from sodium aluminate and sodium metasilicate nonahydrate has a suitable specific surface area and micropore volume for adsorbing CO2, and has a good CO2 adsorption capacity.

[0045] In one embodiment, in S20, the reaction temperature is 25°C to 45°C, and in S30, the hydrothermal reaction temperature is 80°C to 100°C.

[0046] In one embodiment, the calcination temperature is 400°C to 600°C.

[0047] In one embodiment, the second duration is 8 hours to 12 hours, and the third duration is 2 hours to 6 hours.

[0048] In one embodiment, the first duration is 20 to 30 hours.

[0049] The 13X molecular sieve prepared by the above-described synthesis method has micropores of 0.6-1.4 nm accounting for more than 70% of the total pore volume.

[0050] The molecular sieve prepared by the above-described synthesis method for 13X molecular sieve has a CO2 adsorption capacity of 6.23 mmol / g or higher and a carbon dioxide / nitrogen selectivity ratio of 57 or higher.

[0051] It is worth noting that the process temperature and process time involved in the above embodiments are all temperatures or times used in the experiment. Any reasonable adjustments made by those skilled in the art based on the process temperature and process time provided by the present invention, within the error range, should be included within the protection scope of the present invention.

[0052] The technical solution and effects of the present invention will be further illustrated below through specific embodiments.

[0053] Main reagents

[0054] Sodium metasilicate nonahydrate (CAS: 13517-24-3), sodium aluminate (CAS: 1302-42-7), and granular NaOH produced by Sinopharm Chemical Reagent Co., Ltd. were all AR-grade chemical reagents. Commercially available 13X type raw powder was purchased from Shanghai Jiuzhou Chemical Co., Ltd.

[0055] Examples 1-3

[0056] Synthesis of 13X molecular sieve:

[0057] 1.5 g of granular NaOH was added to 14.8 ml of water and stirred at room temperature for 10 min to obtain a homogeneous solution, i.e., sodium hydroxide solution; 0.5 g of sodium aluminate was added to 3.85 ml of water and stirred at room temperature for 10 min to obtain a homogeneous sodium aluminate solution; 3.81 g of sodium metasilicate nonahydrate was added to 9.7 ml of water and stirred at room temperature for 10 min to obtain a homogeneous sodium metasilicate nonahydrate solution.

[0058] Then, slowly add sodium aluminate solution to sodium hydroxide solution and continue stirring for 5 minutes. Finally, slowly add sodium metasilicate nonahydrate solution to the above solution to obtain the reaction solution.

[0059] The above reaction solution was stirred for 24 hours at different temperatures (25℃, 45℃, 60℃) to obtain a reaction gel;

[0060] The reaction gel was placed in a hydrothermal reactor and hydrothermally reacted at 80°C for 12 hours. Then, it was filtered through a vacuum filtration flask and a polytetrafluoroethylene organic filter membrane. After washing three times, a white solid was obtained. The solid was then dried in an 80°C drying oven for 30 minutes to obtain the reactant.

[0061] The reactants were calcined at 500°C for 4 hours in a tube furnace under nitrogen protection to obtain 13X molecular sieves under different synthesis conditions, which were labeled as Sample 1 (R-25, H-80, H-12, or C-500 are all Sample 1), Sample 2 (R-45), and Sample 3 (R-60).

[0062] Examples 4-6

[0063] The same synthesis method as in Example 1 was used, except that the reaction temperature was 25°C, and the hydrothermal reaction temperatures were 60°C, 100°C, and 120°C, respectively. The synthesized 13X molecular sieve samples were labeled as Sample 4 (H-60), Sample 5 (H-100), and Sample 6 (H-120), respectively.

[0064] Examples 7-9

[0065] The same synthesis method as in Example 1 was used, except that the reaction temperature was 25°C, the hydrothermal reaction temperature was 100°C, and the second reaction time was 8h, 14h, and 16h, respectively. The synthesized 13X molecular sieve samples were labeled as Sample 7 (H-8), Sample 8 (H-14), and Sample 9 (H-16), respectively.

[0066] Examples 7-10

[0067] The same synthesis method as in Example 1 was used, except that the reaction temperature was 25°C, the hydrothermal reaction temperature was 100°C, the second reaction time was 12 hours, and the calcination temperatures were 400°C, 600°C, 700°C, and 800°C, respectively. The synthesized 13X molecular sieve samples were labeled as Sample 10 (C-400), Sample 11 (C-600), Sample 12 (C-700), and Sample 13 (C-800), respectively.

[0068] 1. Sample morphology and particle size detection:

[0069] The crystal structure of the sample was analyzed using a DX-2700 X-ray diffractometer with Cu-Ka radiation. The XRD pattern of the synthesized 13X molecular sieve sample can be found in [link to XRD pattern]. Figure 1 .

[0070] The crystal structure of the samples was analyzed using scanning electron microscopy (SEM). The XRD pattern of the synthesized 13X molecular sieve sample can be found in [link to SEM image]. Figure 2 .

[0071] The CO2 adsorption capacity of the samples was determined using a Quantachrome automatic physico-chemical adsorption instrument (Autosorb-1Q) at 25℃. The results are shown in Table 1.

[0072] Table 1

[0073] As shown in Table 1, keeping other reaction conditions constant and only changing the reaction temperature, the synthesized 13X molecular sieve samples exhibited significant differences in performance, with sample 3 showing the lowest CO2 adsorption capacity. Samples 1 and 2 showed relatively small differences, both ranging from 6 to 7 mmol / g. However, sample 2 required a reaction temperature of 45℃, necessitating heating and a reaction time of 20 to 30 hours, resulting in substantial energy consumption. Sample 1, on the other hand, had a reaction temperature of 25℃, equivalent to room temperature, requiring no additional cooling or heating and thus consuming no extra energy. Therefore, considering both optimal CO2 adsorption capacity and low energy consumption, 25℃ was chosen as the reaction temperature.

[0074] When only the hydrothermal reaction temperature is changed, the CO2 adsorption capacity of the synthesized 13X molecular sieve samples is shown in Table 1. It can be seen that when the hydrothermal reaction temperature of sample 5 is 100℃, its CO2 adsorption capacity is the largest, which is 6.23 mmol / g. Therefore, 100℃ is the preferred hydrothermal reaction temperature.

[0075] The duration of the hydrothermal reaction has different effects on the performance of the synthesized 13X molecular sieve. Among them, sample 5, which has a hydrothermal reaction time of 12 hours, has the largest CO2 adsorption capacity of 13X molecular sieve, which is 6.23 mmol / g. Therefore, 12 hours is the preferred hydrothermal reaction time.

[0076] As can be seen from Table 1 above, the CO2 adsorption capacity of the synthesized 13X molecular sieve samples varies greatly depending on the calcination temperature. Both excessively high and low calcination temperatures have an adverse effect on CO2 absorption capacity. Only a suitable temperature can achieve good CO2 absorption capacity. Among them, sample 5, calcined at 500℃, has the highest CO2 adsorption capacity of 6.23 mmol / g. Therefore, 500℃ is the preferred calcination temperature.

[0077] Depend on Figure 1 As shown in the X-ray diffraction (XRD) patterns, all 13X molecular sieve samples exhibited diffraction peaks highly matched with the FAU-type zeolite structure (PDF#38-0237), with characteristic peaks corresponding to the (111), (220), (311), (331), (533), (642), and (751) crystal planes at 2θ of 6.1°, 9.9°, 11.7°, 15.4°, 23.3°, 26.6°, and 31.0°, respectively. X-ray diffraction (XRD) analysis confirmed that the crystallization temperature has a more significant impact on the crystallization process of the prepared zeolite than the calcination temperature, because the crystallization temperature directly regulates the nucleation rate of the zeolite framework and the crystal growth kinetics, thereby affecting the crystallinity and phase purity of the final product. In contrast, the main function of calcination temperature is to remove residual impurities in the synthesized zeolite. Its influence is usually limited to adjusting the pore structure rather than interfering with the basic crystallization process of zeolite. Therefore, crystallization temperature is the dominant factor in regulating the formation of the zeolite framework. Zeolites prepared under different crystallization times and reaction temperatures all exhibit excellent crystallinity, indicating that the above-mentioned key synthesis parameters did not have a significant adverse effect on the crystallization process.

[0078] Depend on Figure 2The microstructure of all 13X molecular sieve samples and C-13X zeolite was analyzed using scanning electron microscopy (SEM). SEM images showed that all synthesized 13X zeolite particles exhibited an octahedral structure. Notably, the surface morphology of the zeolite underwent a significant evolution with increasing crystallization temperature: its surface initially became smooth and angular, then gradually became rough, accompanied by blunting of the edges (Fig. 2a-c). Extending the crystallization time also led to changes in the zeolite morphology (Fig. 2d, a, ef), with the sample crystallized for 12 h showing the clearest outline (Fig. 2a). In contrast, the reaction temperature had a more significant effect on the zeolite surface morphology (Fig. 2a, gh). When the reaction temperature increased from 25 ℃ to 60 ℃, the zeolite surface morphology first evolved towards increased smoothness and more prominent edges, then the crystal outline gradually became blurred and broke into irregular non-octahedral structures (Fig. 2h). This two-stage evolution reflects the temperature dependence of gel solubility on crystal growth kinetics: suitable temperatures promote ordered crystal growth, while excessively high temperatures destroy the integrity of the crystal structure. The influence of calcination temperature on zeolite morphology shows a similar trend to crystallization time (Figs. 2i, a, jl), with the sample calcined at 500 ℃ exhibiting the clearest profile (Fig. 2a). In contrast, crystallization time primarily affects crystal maturity without altering its basic morphological characteristics, while calcination temperature only plays a secondary modifying role on the zeolite surface within a narrow optimal temperature range.

[0079] Size measurements were performed on all 13X molecular sieve samples, and the average diameter was calculated. When the crystallization temperature increased from 80 ℃ to 120 ℃, the average diameter exhibited a non-monotonic trend, and the H-100 sample showed the narrowest particle size distribution (sharpest peak), achieving optimal particle uniformity. When the reaction temperature increased from 25 ℃ to 60 ℃, the average diameter also showed a characteristic of first decreasing and then increasing, and the particle size distribution significantly broadened. In contrast, the control effect of crystallization time and calcination temperature on particle size evolution was relatively weak; therefore, the H-100 sample had a uniform particle size distribution, which is beneficial for carbon dioxide adsorption.

[0080] Using commercially available reference material C-13X as a comparison, the nitrogen adsorption-desorption and pore size distribution of 13X molecular sieves prepared from samples 1-13 were tested. The nitrogen adsorption-desorption isotherms are shown below. Figure 3 As shown, and the aperture distribution diagram as shown Figure 4 As shown.

[0081] The pore structure parameters of the 13X molecular sieve prepared from samples 1-13 and the reference material C-13 are shown in Table 2.

[0082] Table 2

[0083] Smicro = t-plot the surface area of ​​the micropores.

[0084] Smicro / SBET = the ratio of the specific surface area of ​​micropores.

[0085] Vtotal = Total pore volume of single-point adsorption calculated from the nitrogen adsorption amount when P / P0=0.997.

[0086] Vmicro = The micropore volume calculated from nitrogen adsorption at P / P0=0.1 (t-plot method).

[0087] The ratio of micropore volume to total pore volume is called the micropore percentage.

[0088] APD stands for Adsorption / Desorption Average Pore Size.

[0089] Depend on Figure 3 , 4 Table 2 shows that, except for samples 4 (H-60), 3 (R-60), 12 (C-700), and 13 (C-800), the 13X molecular sieves prepared from samples 1-13 all exhibited typical type I adsorption behavior, indicating that they have a pure microporous structure. Table 2 also shows that with increasing crystallization temperature, the specific surface area (SBET), micropore surface area (Smicro), micropore volume (Vmicro), and total pore volume (Vtotal) all exhibit a volcanic-like trend, reaching their maximum values ​​of 731.6 m³ / s at a reaction temperature of 25 °C, a calcination temperature of 500 °C, a crystallization temperature of 100 °C, and a crystallization time of 12 h. 2 / g、673.48 m 2 g, 0.257cm 3 / g and 0.336 cm 3 / g, and the 13X molecular sieve structure prepared from samples 1-13 is dominated by micropores of 0.6-1.4 nm, accounting for more than 70% of the total pore volume (with virtually no mesopores). In contrast, C-13X exhibits a mesoporous distribution in the 2-5 nm range. Further confirmation shows that H-100 has superior pore structure parameters (Table 2), with SBET, Smicro, Smicro / SBET, Vtotal, Vmicro, and Vmicro / Vtotal all higher than C-13X, and a smaller APD (1.836 nm vs 1.868 nm), indicating a finer pore size.

[0090] In existing technologies, the 13X zeolite samples prepared by Liu, J., Sun, X., Li, N., Tan, T., Zhang, F., Sun, M., &Liu, Q. exhibit excellent structural parameters (specific surface area 720.8 m²). 2 / g, pore volume 0.458 cm³ 3 However, under conditions of 25 °C and 1 bar, its CO2 adsorption capacity was measured to be only 2.69 mmol / g by static volumetric method, which is far lower than the theoretical adsorption potential corresponding to its high structural parameters, indicating that its micropore specific surface area (Smicro) and micropore volume (Vmicro) ratio are insufficient.

[0091] 2.13X Molecular Sieve Selectivity Experiment

[0092] Commercially available reference material C-13X was selected as a comparison, and the samples in the embodiments of this application were used as the research objects (among which the best-performing sample 5 was labeled H-100). The carbon dioxide adsorption capacity of the samples was systematically evaluated by measuring the single-component gas adsorption isotherms at two representative temperatures (0°C and 25°C) and 1 bar. The adsorption and selectivity performance evaluation methods are as follows:

[0093] Adsorption experiments were conducted on a Quantachrome automated physicochemical adsorption analyzer (Autosorb-1Q) to measure the adsorption capacity of 13X zeolite for CO2 or N2 under different synthesis conditions. Ultra-high purity CO2 or N2 was used in the experiments. Before measurement, 0.1 g of 13X sample was loaded into a sample tube and vacuum-treated at 200°C for 10 hours. After cooling to room temperature, the tube was filled with nitrogen. The sample tube was then transferred to the test station for CO2 or N2 adsorption experiments under different conditions. The static saturated adsorption capacity (qads, mmol / g) of CO2 and N2 was calculated using the volumetric method. Saturated adsorption capacity was defined according to Formula 1. Where V is the volume of adsorbed CO2, in cm³ / g; V m It is 22.4 L / mol; T is the adsorption temperature in K; T0 is 273 K.

[0094] like Figure 5As shown in a~h. It is noteworthy that H-100 exhibits the highest carbon dioxide adsorption capacity at 0°C and 1 bar, at 7.38 mmol / g, exceeding that of materials synthesized under other preparation conditions (such as...). Figure 5 (As shown in Table 3). In contrast, nitrogen adsorption showed negligible absorbance values ​​(less than 0.15 mmol / g for H-100 at 25°C and 1 bar, as shown in Table 3), highlighting its significantly superior selectivity for carbon dioxide compared to nitrogen.

[0095] The Ideal Adsorption Solution Theory (IAST) is used to evaluate the adsorption capacity of binary gases such as carbon dioxide and nitrogen based on the adsorption results of single-component gases, and to determine the selectivity factor S of the binary mixture using isotherm data of the pure components. ads Based on the adsorption isotherms of CO2 and N2 at 1 Pa, the selectivity of carbon dioxide / nitrogen was calculated using the Ideal Adsorption Solution Theory (IAST). Figure 6 (a~e). The selectivity factor is defined according to Formula 2, where q i It represents the amount of CO2 or N2 adsorbed, expressed in millimoles per gram (mmol / g).

[0096] ;

[0097] Compared to the adsorption capacities of carbon dioxide and nitrogen (at 273 K and 298 K), both are higher than those of H-100. Meanwhile, the calculated carbon dioxide / nitrogen selectivity ratio reaches 149, which is 1.98 times higher than the benchmark material C-13X (data shown in Table 3).

[0098] Table 3 Adsorption performance and selectivity of H-100 and C-13X for carbon dioxide and nitrogen

[0099] 3. Cyclic stability experiment of 13X molecular sieve

[0100] The cyclic stability of the molecular sieve was studied using an adsorption-regeneration cycle test.

[0101] 3.1. Automated Physicochemical Adsorption Experiment

[0102] Repeat the adsorption experiment in item 6 above 15 times, that is, 15 cycles.

[0103] 3.2. Thermogravimetric (TG) adsorption-desorption experiments in simulated flue gas (5% carbon dioxide / nitrogen)

[0104] The following content will be repeated 10 times, that is, 10 cycles.

[0105] The carbon dioxide absorption capacity of H-100 was investigated using thermogravimetric analysis (TGA, Netzsch STA449, Germany) under simulated flue gas conditions. First, 55 mg of the sample was heated to 200°C at a rate of 10°C / min in a pure nitrogen atmosphere (flow rate 50 mL / min) and held for 2 hours. It was then cooled to room temperature (25°C) and equilibrated in nitrogen for 1 hour. Regeneration was subsequently achieved by thermal desorption, i.e., heating the saturated adsorbent to 200°C in a pure nitrogen atmosphere (200°C). To assess the suitability of the material, the following experiments were conducted: (1) inlet carbon dioxide concentration (from 5% to 100% carbon dioxide / nitrogen), (2) absorption temperature (25–110°C), and (3) cycle regeneration stability, according to Equation 3.

[0106] m0 represents the initial mass (mg), while m t This indicates the mass (mg) after adsorption.

[0107] Automated physicochemical adsorption experiment ( Figure 7 a) indicates that the sample exhibited stable adsorption-regeneration performance over 15 cycles, with no significant decrease in adsorption capacity. At 25°C and 1 bar, the adsorption capacity for carbon dioxide reached 6.0 mmol / g. Thermogravimetric (TG) adsorption-desorption experiments in simulated flue gas (5% carbon dioxide / nitrogen) showed that the adsorption capacity of H-100 gradually decreased from 2.98 mmol / g to 2.78 mmol / g after 10 cycles, and then tended to stabilize. Figure 7 (b) These results demonstrate that H-100 exhibits good stability under both static and dynamic adsorption conditions. Therefore, in this study, the H-100 molecular sieve (i.e., the 13X molecular sieve of sample 5) prepared under appropriate synthesis conditions can achieve satisfactory carbon dioxide capture capacity and excellent regeneration recovery capacity, which has practical application significance.

[0108] 4. Dynamic penetration test evaluation

[0109] The separation performance of H-100 and C-13X for CO2 / N2 mixtures was evaluated by dynamic breakthrough experiments. Figure 8 , 9 A breakthrough experiment was conducted using a CO2 / N2 adsorbate mixture with a volume composition of 10:90. The dynamic CO2 adsorption capacity at any time t was calculated using Equation 4. A blank experiment was performed using an empty quartz tube reactor before each breakthrough experiment to determine and subtract the dead volume of the system. The breakthrough time observed in the experiment was defined as the moment when the normalized concentration of CO2 or N2 at the outlet (C / C0) reached adsorption equilibrium (C / C0 = 1).

[0110] ;

[0111] q is the CO2 capture capacity (mmol / g), Cin and Cout are the inlet and outlet CO2 concentrations (vol.%), m is the sample mass (g), and Q is the flow rate (mL / min).

[0112] The results showed that the CO2 adsorption capacity was optimal when the sample volume was 300 mg and the flow rate was 40 mL / min (Figure 8d). With increasing temperature (30-80 ℃), the adsorption capacity decreased, and both breakthrough time and saturation time shortened. During the experiment, N2 was detected immediately, while CO2 breakthrough was delayed, resulting in a "roll-up area"—the N2 concentration at the outlet was temporarily higher than the feed concentration before the column was fully saturated. The breakthrough time interval between CO2 and N2 in H-100 was significantly longer than that in C-13X, indicating that H-100 (3.52 mmol / g) had better CO2 adsorption and separation performance than C-13X (3.11 mmol / g).

[0113] The above-disclosed embodiments are merely preferred embodiments of the present invention and should not be construed as limiting the scope of the invention. Those skilled in the art will understand that implementing all or part of the above-described embodiments and making equivalent changes in accordance with the claims of the present invention are still within the scope of the invention.

Claims

1. A method for synthesizing 13X molecular sieve, characterized in that, Includes the following steps: S10. Mix sodium aluminate solution, sodium hydroxide solution, and sodium metasilicate nonahydrate solution and stir until homogeneous to obtain a reaction solution; S20. The reaction solution is stirred at the reaction temperature for a first time to obtain a reaction gel; wherein the reaction temperature is 25°C to 60°C to allow crystals to grow in an orderly manner. S30. The reaction gel is subjected to hydrothermal reaction at a hydrothermal reaction temperature for a second time, then filtered and dried to obtain the reactant; wherein the hydrothermal reaction temperature is 80°C to 120°C to adjust the nucleation rate of the zeolite framework, crystal growth orientation and selective development of crystal faces. S40. The reactants are calcined in an inert gas atmosphere at 400°C to 800°C for a third time to remove residual impurities and adjust the pore structure to obtain 13X molecular sieve.

2. The method for synthesizing 13X molecular sieve as described in claim 1, characterized in that, In step S10, sodium aluminate solution and sodium metasilicate nonahydrate solution are added dropwise to sodium hydroxide solution under stirring conditions, with a stirring rate of 500~700 r / min.

3. The method for synthesizing 13X molecular sieve as described in claim 2, characterized in that, The mass ratio of sodium aluminate, sodium hydroxide, and sodium metasilicate nonahydrate is 1:1-5:5-10.

4. The method for synthesizing 13X molecular sieve as described in claim 1, characterized in that, In step S20, the reaction temperature is 25°C to 45°C, and in step S30, the hydrothermal reaction temperature is 80°C to 100°C.

5. The method for synthesizing 13X molecular sieve as described in claim 4, characterized in that, The calcination temperature is 400℃ to 600℃.

6. The method for synthesizing 13X molecular sieve as described in claim 1 or 5, characterized in that, The second duration is 8 to 12 hours, and the third duration is 2 to 6 hours.

7. The method for synthesizing 13X molecular sieve as described in claim 1, characterized in that, The first duration is 20 to 30 hours.

8. The method for synthesizing 13X molecular sieve as described in claim 2, characterized in that, The concentration of the sodium aluminate solution is 1.22 mol / L, the concentration of the sodium hydroxide solution is 2.5 mol / L, and the concentration of the sodium metasilicate nonahydrate solution is 1.34 mol / L.

9. The 13X molecular sieve prepared by the synthesis method of any one of claims 1-8, wherein the micropores of 0.6-1.4 nm account for more than 70% of the total pore volume in the 13X molecular sieve.

10. The molecular sieve prepared by the synthesis method of 13X molecular sieve according to any one of claims 1-8 is used in CO2 adsorption, wherein the CO2 adsorption capacity is 6.23 mmol / g or higher, and the carbon dioxide / nitrogen selectivity ratio is 57 or higher.

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