Preparation method of modified 13X molecular sieve for improving adsorption performance and selectivity

Abstract

A preparation method of modified 13X molecular sieve for improving adsorption performance and selectivity. In this method, a predetermined amount of deionized water is added to a predetermined amount of sodium source and aluminum source to obtain mixed solution A and mixed solution B; mixed solution A and mixed solution B are mixed to obtain mixed solution C; a predetermined amount of metal salt is added to mixed solution C to obtain mixed solution D, ensuring that the metal ions are evenly distributed in the precursor solution without the need for a template agent; a predetermined amount of silicon source is added to mixed solution D, and after continuous stirring for a predetermined time, a gel is obtained, ensuring that the metal does not block the pores, so as to form a 13X molecular sieve with high crystallinity and gadolinium spray microporosity. After hydrothermal crystallization, filtration, washing, drying, and calcination, a heteroatom-modified 13X molecular sieve is obtained. In this way, while ensuring that the metal does not block the pores of the 13X molecular sieve, the micropore aperture of the 13X molecular sieve is effectively narrowed, and the adsorption performance and selectivity of the 13X molecular sieve are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of carbon dioxide capture functional materials, and particularly to a preparation method of modified 13X molecular sieve for improving adsorption performance and selectivity performance. Background Art

[0002] A series of environmental problems caused by the continuous intensification of global warming have attracted the high attention of the whole society to anthropogenic carbon dioxide emissions. Carbon capture and storage (CCS) technology is an effective way to realize the separation, recovery and comprehensive utilization of CO 2 and can effectively alleviate the above crisis. Among them, the design and preparation of solid adsorbents are the core of this technology.

[0003] Common solid adsorbents include activated carbon, molecular sieve, metal-organic framework (MOFs) and mesoporous silica materials. 13X molecular sieve has been commercially applied to CO 2 adsorption and separation due to its characteristics such as low cost, stability and easy preparation. However, based on the differences in molecular size and the strength of physical adsorption, it cannot efficiently adsorb and separate CO 2 . Therefore, it is necessary to decorate the structure and surface of the molecular sieve to improve the adsorption performance and selectivity performance of the molecular sieve for CO 2 . Summary of the Invention

[0004] In view of this, it is necessary to provide a preparation method of modified 13X molecular sieve for improving adsorption performance and selectivity performance.

[0005] A preparation method of modified 13X molecular sieve for improving adsorption performance and selectivity performance includes the following steps:

[0006] Add a predetermined amount of deionized water to a predetermined amount of sodium source and aluminum source respectively at a predetermined temperature, and stir evenly to obtain mixed solution A and mixed solution B;

[0007] Mix mixed solution A and mixed solution B, and stir evenly to obtain mixed solution C;

[0008] Add a predetermined amount of transition metal salt to mixed solution C, and stir evenly to obtain mixed solution D, so that the transition metal salt is dispersed simultaneously with framework aluminum and sodium ions in mixed solution D as a precursor liquid, ensuring that the metal ions are evenly distributed in the precursor liquid without the need for a template agent;

[0009] Add a predetermined amount of silicon source to mixed solution D, and continuously stir for a predetermined time to form a gel solution containing transition metal ions. Among them, the silicon source is used to adjust the amount of transition metal ions entering the 13X molecular sieve framework, ensuring that the metal ions do not block the pores to form a gel solution containing transition metal ions;

[0010] Place the obtained gel solution in a stainless-steel autoclave and hydrothermally crystallize it at a predetermined temperature for a predetermined time;

[0011] After the crystallization reaction, filter, wash, dry, and calcine to obtain heteroatom-modified 13X molecular sieve.

[0012] In the above method for preparing modified 13X molecular sieve with improved adsorption performance and selectivity, add a predetermined amount of deionized water to a predetermined amount of sodium source and aluminum source respectively at a predetermined temperature, and stir evenly to obtain mixed solution A and mixed solution B; mix mixed solution A and mixed solution B and stir evenly to obtain mixed solution C; add a predetermined amount of metal salt to mixed solution C and stir evenly to obtain mixed solution D, so that the transition metal salt is dispersed simultaneously with framework aluminum and sodium ions in mixed solution D as the precursor liquid, ensuring that the metal ions are evenly distributed in the precursor liquid without the need for a template agent; add a predetermined amount of silicon source to mixed solution D, and continue to stir for a predetermined time to obtain a gel solution containing transition metal ions. Among them, the silicon source is used to adjust the amount of transition metal ions entering the 13X molecular sieve framework, ensuring that the metal ions do not block the pores to form a gel solution containing transition metal ions. After hydrothermal crystallization, filtration, washing, drying, and calcination, heteroatom-modified 13X molecular sieve is obtained. In this way, while ensuring that the metal does not block the pores of the 13X molecular sieve, the micropore aperture of the 13X molecular sieve is effectively narrowed, and the adsorption performance and selectivity of the 13X molecular sieve are improved. Description of the Drawings

[0013] Figure 1 Figures (a) and (b) are respectively the scanning electron microscope (SEM) and energy-dispersive X-ray spectroscopy mapping (EDS-Mapping) images of the Cu / Fe heteroatom-containing 13X molecular sieves obtained in Example 1 and Example 2.

[0014] Figure 2 Figures (a) and (b) are respectively the transmission electron microscope (TEM) images of the Cu / Fe heteroatom-containing 13X molecular sieves obtained in Example 1 and Example 2.

[0015] Figure 3 Are the FT-IR spectra of the Cu / Fe heteroatom-containing 13X molecular sieves obtained in Example 1 and Example 2.

[0016] Figure 4 Figures (a) and (b) are respectively the nitrogen adsorption / desorption curves of the Cu / Fe heteroatom-containing 13X molecular sieves obtained in Example 1 and Example 2 at 77K and the narrow micropore size distribution (NMPSD) plots obtained from the CO adsorption isotherm at 273K 2 Adsorption isotherm.

[0017] Figure 5CO adsorption curves of the Cu / Fe heteroatom-containing 13X molecular sieves obtained in Example 1 and Example 2 at 25 °C. 2 Adsorption curve graph.

[0018] Figure 6 Binary breakthrough adsorption curves of the Cu / Fe heteroatom-containing 13X molecular sieves obtained in Example 1 and Example 2 in simulated flue gas at 60 °C (15% CO 2 / 85% N 2 ). Detailed implementation manners

[0019] In the method for preparing the modified 13X molecular sieve with improved adsorption performance and selectivity provided by the present invention, readily available and inexpensive raw materials and a simple process are used to in-situ construct heteroatoms (such as Cu, Fe) in the 13X molecular sieve framework, and while ensuring that metal ions do not block the pores of the 13X molecular sieve, the micropore aperture of the 13X molecular sieve is effectively narrowed. To enable those skilled in the art to better understand the above method, the above method is described in detail below.

[0020] A method for preparing a modified 13X molecular sieve with improved adsorption performance and selectivity, comprising the following steps:

[0021] Step S100, adding a predetermined amount of deionized water to a predetermined amount of sodium source and aluminum source respectively at a predetermined temperature, and stirring evenly to obtain mixed solution A and mixed solution B; wherein, the aluminum source is one or more of sodium aluminate, aluminum sol, and aluminum sulfate; the sodium source is one or more of sodium hydroxide and sodium peroxide.

[0022] Step S103, mixing mixed solution A and mixed solution B and stirring evenly to obtain mixed solution C.

[0023] Step S105, adding a predetermined amount of transition metal salt to mixed solution C, stirring evenly to obtain mixed solution D, so that the transition metal salt is dispersed simultaneously with framework aluminum and sodium ions in mixed solution D as a precursor liquid, ensuring that metal ions are evenly distributed in the precursor liquid without the need for a template agent; wherein, the metal salt is ferric nitrate nonahydrate or copper nitrate hexahydrate. The stirring time can be 1 to 4 h.

[0024] Step S107: Add a predetermined amount of silicon source to the mixed solution D, and continuously stir for a predetermined time to obtain a gel solution containing transition metal ions. Herein, the silicon source is used to adjust the amount of transition metal ions entering the 13X molecular sieve framework to ensure that the metal ions do not block the pores, so as to form a gel solution containing transition metal ions. Wherein, the silicon source is one or more of silica, sodium silicate, and silica sol, and the stirring time is 6 - 10 h. When the metal salt is a Cu salt, the molar ratio of the silicon source : sodium source : deionized water : aluminum source : metal salt is respectively 1 SiO 2 / 0.58 Na 2 O / 33H 2 O / 0.06 Al 2 O 3 / (0.01 - 0.1)% Cu; when the metal salt is an Fe salt, the molar ratio of the silicon source : sodium source : deionized water : aluminum source : metal salt is respectively 1 SiO 2 / 0.58 Na 2 O / 33 H 2 O / 0.06 Al 2 O 3 / (0.01 - 0.1)% Fe.

[0025] Step S109: Place the obtained gel solution in a stainless - steel autoclave and carry out hydrothermal crystallization for a predetermined time at a predetermined temperature. Wherein, the hydrothermal crystallization time is 12 - 16 h, and the hydrothermal crystallization temperature is 80 - 100 °C.

[0026] Step S111: After the crystallization reaction, carry out filtration, washing, drying, and calcination to obtain the heteroatom - modified 13X molecular sieve. Wherein, the drying time is 24 - 36 h, and the calcination temperature is 500 - 600 °C.

[0027] The above - mentioned method is further illustrated by the following examples: Example 1

[0028] Prepare a Cu - heteroatom - modified 13X molecular sieve, and its preparation method includes the following steps:

[0029] (1) At room temperature, add 1.5 g of NaOH and 0.5 g of Na 2 Al 2 O 4 to two 50 - ml beakers respectively, and fully mix with 10 ml of deionized water to obtain mixed solutions A and B.

[0030] (2) Inject the mixed solutions A and B in step (1) into a 100 - ml beaker simultaneously and stir evenly to obtain a mixed solution C. For example, the stirring time is 15 min.

[0031] (3) Add 0.09 g of Cu(NO 3 ) 3 ·6H 2 O to the mixed solution C, stir for 1 h to obtain the mixed solution D.

[0032] (4) Slowly add 3.81 g of an aqueous solution of Na 2 SiO 3 ·9H 2 O to the mixed solution D to obtain a gel solution, and continuously stir for 6 h; for example, use a dropping funnel to control the dropping rate of the silicon source at 1 drop per 2 seconds for dropping.

[0033] (5) Place the gel solution in a 100 ml stainless steel autoclave, crystallize at 80 °C for 14 h, and cool to room temperature.

[0034] (6) Wash the product with deionized water until neutral, and dry it in vacuum to obtain light blue (Cu@13X) powder.

[0035] (7) Place the powder in a muffle furnace and calcine it in an N 2 atmosphere at 500 °C for 4 h to obtain the final product Cu@13X molecular sieve. Example 2

[0036] Prepare a modified 13X molecular sieve containing Fe heteroatoms, and its preparation method includes the following steps:

[0037] (1) At room temperature, add 1.5 g of NaOH and 0.5 g of Na 2 Al 2 O 4 to another 50 ml beaker respectively, and mix well with 10 ml of deionized water to obtain the mixed solutions A and B.

[0038] (2) Inject the mixed solutions A and B in step (1) into a 100 ml beaker simultaneously, and stir evenly to obtain the mixed solution C.

[0039] (3) Add 0.09 g of Fe(NO 3 ) 3 ·9H 2 O to the mixed solution C, stir for 1 h to obtain the mixed solution D.

[0040] (4) Slowly add 3.81 g of an aqueous solution of Na 2 SiO 3 ·9H 2 O to the mixed solution D to obtain a gel solution, and continuously stir for 6 h; for example, use a dropping funnel to control the dropping rate of the silicon source at 1 drop per 2 seconds for dropping.

[0041] (5) Place the gel solution in a 100 ml stainless steel high-pressure reactor, crystallize at 80 °C for 14 h, and cool to room temperature.

[0042] (6) Wash the product with deionized water until neutral, and dry it under vacuum to obtain light yellow (Fe@13X) powder.

[0043] (7) Place the powder in a muffle furnace and calcine it in an N 2 atmosphere at 500 °C for 4 h to obtain the final product Fe@13X molecular sieve.

[0044] Verification of the adsorption and selectivity of Cu@13X molecular sieve and Fe@13X molecular sieve:

[0045] 1. Performance characterization of Cu@13X and Fe@13X molecular sieves.

[0046] (1) Scanning electron microscopy (SEM) and energy dispersive spectroscopy mapping (EDS~Mapping) analysis. Please refer to Figure 1 , Figure 1 Figures (a) and (b) in which are the SEM and EDS~Mapping test results of Cu@13X and Fe@13X molecular sieves respectively. The molecular sieves both have an octahedral structure and an approximately circular appearance, which is consistent with the typical crystallization state of 13X, indicating that the prepared Cu@13X and Fe@13X have good dispersibility and high crystallinity, and the heteroatoms do not affect the framework structure of the molecular sieve. In addition, the heteroatoms Cu and Fe are evenly distributed in the molecular sieve crystal.

[0047] (2) Transmission electron microscopy (TEM) analysis. Please refer to Figure 2 , Figure 2 Figures (a) and (b) in which are the SEM images of Cu@13X and Fe@13X molecular sieves respectively. The results are consistent with those of the scanning electron microscopy, and the heteroatoms do not affect the framework structure of the molecular sieve.

[0048] (3) Fourier transform infrared (FT~IR) analysis. Please refer to Figure 3 , Figure 3 Figures in which are the FTIR spectra of 13X, Cu@13X and Fe@13X molecular sieves in sequence. The results show that all samples have obvious absorption peaks at 981, 756, 679, 567 and 467 cm ~1 . This is consistent with the FTIR spectrum of 13X. 467 cm ~1The peak at [frequency] is caused by the bending vibration of metal-oxygen (M-O), and the peak at 756 cm⁻¹ is caused by the Si(Al)-O vibration. However, the intensities of the stretching vibration peaks of Fe@13X and Cu@13X at 467 and 981 cm⁻¹ are significantly stronger than those of 13X, indicating that Fe 3+ and Cu 2+ occupy the T-sites of the 13X framework, resulting in an increased electronegativity difference between the atoms connected at both ends of the chemical bond, thus leading to stronger absorption vibration peaks.

[0049] (4) For the nitrogen adsorption-desorption isotherms and pore size analysis at 77 K, please refer to Figure 4 and Figure 4 simultaneously. Figures (a) and (b) in [[reference]] are the nitrogen adsorption-desorption isotherms and pore size diagrams of 13X, Cu@13X, and Fe@13X zeolites at 77 K, respectively. The results show that the specific surface areas of 13X, Cu@13X, and Fe@13X zeolites are 881 m 2 / g, 850 m 2 / g, and 734 m 2 / g, respectively. The pore sizes mainly extend towards the direction of smaller pore sizes, indicating that Cu 2+ and Fe 3+ in the framework effectively narrow the microporous channels of 13X.

[0050] 2. The static and dynamic CO 2 adsorption performances of Cu@13X and Fe@13X zeolites were measured using an automatic physical adsorption analyzer (Autosorb-IQ) and a fixed-bed adsorption device, respectively. 2

[0051] (1) Static CO 2 adsorption performance test

[0052] Please refer to Figure 5 and Figure 5 simultaneously. Figures in [[reference]] are the CO 2 adsorption curves of 13X, Cu@13X, and Fe@13X zeolites at 25 °C, respectively. The results show that the CO 2 adsorption capacities of Cu@13X and Fe@13X are 6.95 mmol / g and 7.66 mmol / g, respectively, which are higher than 5.79 mmol / g of 13X, indicating that heteroatoms Cu / Fe can effectively improve the adsorption performance of the zeolite.

[0053] (2) Dynamic CO 2 adsorption performance test

[0054] Please refer to Figure 6 and Figure 6 simultaneously. Figure in [[reference]] is for the zeolite in simulated flue gas at 60 °C (15% CO 2 / 85% N2 ) binary breakthrough adsorption curve, and the results show that compared with 13X, the breakthrough time of Cu@13X and Fe@13X is longer, that is, CO 2 has better adsorption performance, reaching 1.60 mmol / g and 1.65 mmol / g, higher than 1.1 mmol / g of 13X, indicating that heteroatoms Cu / Fe can effectively improve the adsorption performance and selectivity of molecular sieves.

Claims

1. A preparation method of modified 13X molecular sieve for improving adsorption performance and selectivity, which is characterized in that, it includes the following steps: Add a predetermined amount of deionized water to a predetermined amount of sodium source and aluminum source respectively at a predetermined temperature, and stir evenly to obtain mixed solution A and mixed solution B; Mix mixed solution A and mixed solution B, and stir evenly to obtain mixed solution C; Add a predetermined amount of transition metal salt to mixed solution C, and stir evenly to obtain mixed solution D, so that the transition metal salt is dispersed simultaneously with framework aluminum and sodium ions in mixed solution D as a precursor liquid, ensuring that the metal ions are evenly distributed in the precursor liquid without the need for a template agent. Among them, the metal salt is ferric nitrate nonahydrate or copper nitrate hexahydrate; Add a predetermined amount of silicon source to mixed solution D, and continuously stir for a predetermined time to obtain a gel liquid containing transition metal ions. Among them, the silicon source is used to adjust the amount of transition metal ions entering the 13X molecular sieve framework, ensuring that the metal ions do not block the pores to form a gel liquid containing transition metal ions; Place the obtained gel liquid in a stainless steel autoclave and hydrothermally crystallize at a predetermined temperature for a predetermined time; After the crystallization reaction, filtration, washing, drying, and calcination are carried out to obtain heteroatom-modified 13X zeolite; the silicon source is one or more of silica, sodium silicate, and silica sol; the aluminum source is one or more of sodium aluminate, aluminum sol, and aluminum sulfate; the sodium source is one or more of sodium hydroxide and sodium peroxide; the metal salt is ferric nitrate hexahydrate or copper nitrate hexahydrate; the molar ratios of the silicon source:sodium source:deionized water:aluminum source:metal salt are 1 SiO 2 / 0.58 Na 2 O / 33 H 2 O / 0.06 Al 2 O 3 / (0.01 - 0.1)% Cu; the obtained heteroatom-modified 13X zeolite is Cu@13X, and the static CO 2 adsorption capacity of Cu@13X at 25 °C is 6.95 mmol / g, and the dynamic CO 2 adsorption capacity at 60 °C is 1.60 mmol / g; the specific surface area of the Cu@13X zeolite is 850 m 2 / g; the molar ratios of the silicon source:sodium source:deionized water:aluminum source:metal salt are 1 SiO 2 / 0.58 Na 2 O / 33 H 2 O / 0.06 Al 2 O 3 / (0.01 - 0.1)% Fe; the obtained heteroatom-modified 13X zeolite is Fe@13X, and the static CO 2 adsorption capacity of Fe@13X at 25 °C is 7.66 mmol / g, and the dynamic CO 2 adsorption capacity at 60 °C is 1.65 mmol / g; the specific surface area of the Fe@13X zeolite is 734 m 2 / g.

2. The preparation method of modified 13X molecular sieve for improving adsorption performance and selectivity as described in claim 1, which is characterized in that: In the step of "adding a predetermined amount of transition metal salt to mixed solution C and stirring evenly to obtain mixed solution D", the stirring time is 1 h.

3. The preparation method of modified 13X molecular sieve for improving adsorption performance and selectivity as described in claim 1, which is characterized in that: In the step of "adding a predetermined amount of silicon source to mixed solution D and continuously stirring for a predetermined time to obtain a gel", the stirring time is 6 h.

4. The preparation method of modified 13X molecular sieve for improving adsorption performance and selectivity as described in claim 1, which is characterized in that: In the step of "placing the obtained gel in a stainless steel autoclave and hydrothermally crystallizing at a predetermined temperature for a predetermined time", the hydrothermal crystallization time is 12 - 16 h, and the hydrothermal crystallization temperature is 80 - 100 °C.

5. The preparation method of modified 13X molecular sieve for improving adsorption performance and selectivity as described in claim 1, which is characterized in that: In the step of "after the crystallization reaction, filtering, washing, drying, and calcining to obtain a heteroatom-modified 13X molecular sieve", the drying time is 24 - 36 h, and the calcination temperature is 500 - 600 °C.

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