Modified saPO-56 type zeolite molecular sieve, and preparation method and application thereof

Abstract

This invention provides a modified SAPO-56 zeolite molecular sieve, its preparation method, and its applications, relating to the field of chemical adsorbent technology. The invention involves mixing a silicon source, an aluminum source, phosphoric acid, a template agent, and water to obtain an initial reaction gel; crystallizing the initial reaction gel to obtain a SAPO-56 zeolite molecular sieve containing a template agent; mixing the SAPO-56 zeolite molecular sieve with a cation exchange solution for ion exchange; and calcining the resulting ion exchange product to obtain a modified SAPO-56 zeolite molecular sieve; the cations in the cation solution include alkali metal ions or lanthanide rare earth metal ions. The modified SAPO-56 zeolite molecular sieve prepared by this invention has high crystallinity and, compared with the original SAPO-56 molecular sieve powder, exhibits significantly improved CO2 adsorption performance, demonstrating excellent CO2 / N2 gas adsorption and separation performance.

Description

Technical Field

[0001] This invention relates to the field of chemical adsorbent technology, and in particular to a modified SAPO-56 zeolite molecular sieve, its preparation method, and its application. Background Technology

[0002] SAPO-56 molecular sieve, with its AFX-type framework structure, has shown potential applications in gas adsorption separation and some catalytic reactions due to its unique cage-like structure and appropriate pore size.

[0003] For SAPO-56, Moises reported that it exhibits high CO2 cycloaddition catalytic activity due to its excellent CO2 adsorption performance (Dalton Trans. 2013, 42, 6732). Niklas reported that SAPO-56 synthesized using seed crystals had a CO2 adsorption capacity of 4.73 mmol / g and a methane adsorption capacity of 1.08 mmol / g at 273 K (Inorganica Chimica Acta. 2021, 525, 120443). Furthermore, Niklas et al. reported in another paper that the adsorption and separation selectivity of SAPO-56 for CO2 and CH4 was 20–30 (Appl. Energy. 2016, 162, 613-621) (Micropor Mesopor Mater. 2012, 156, 90-96).

[0004] The main components of industrial flue gas are N2 and CO2. In the adsorption and separation technology of industrial flue gas, the selective adsorption of CO2 from N2 has always been a research hotspot and a difficult problem. However, SAPO molecular sieves usually have a low adsorption capacity for CO2 and are not effective in separating flue gas. Summary of the Invention

[0005] In view of this, the purpose of this invention is to provide a modified SAPO-56 zeolite molecular sieve, its preparation method, and its applications. The modified SAPO-56 zeolite molecular sieve prepared by this invention has high crystallinity and excellent CO2 / N2 gas adsorption and separation performance.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0007] This invention provides a method for preparing modified SAPO-56 zeolite molecular sieves, comprising the following steps:

[0008] A silicon source, an aluminum source, phosphoric acid, a template agent, and water were mixed to obtain an initial reaction gel; the template agent was N,N,N',N'-tetramethyl-1,6-hexanediamine.

[0009] The initial reaction gel was crystallized to obtain SAPO-56 zeolite molecular sieve, which contains a template agent.

[0010] The SAPO-56 zeolite molecular sieve is mixed with a cation solution for ion exchange, and the resulting ion exchange product is calcined to obtain a modified SAPO-56 zeolite molecular sieve; the cations in the cation solution include alkali metal ions or lanthanide rare earth metal ions.

[0011] Preferably, the silicon source includes one or more of silica sol, sodium silicate, potassium silicate, and silica; the aluminum source includes one or more of aluminum hydroxide, aluminum oxide, aluminum chloride, aluminum sulfate, sodium aluminate, boehmite, aluminum isopropoxide, and gibbsite.

[0012] Preferably, the silicon source, aluminum source, and phosphoric acid are calculated as SiO2, Al2O3, and P2O5, respectively, and the molar ratio of the silicon source, aluminum source, phosphoric acid, template agent, and water is (0.2-1):(0.5-1):0.37:(2-3):(20-100).

[0013] Preferably, the crystallization temperature is 150–220°C and the time is 2–6 days.

[0014] Preferably, the alkali metal ion includes Li + Na + K + and Cs + One or more of the lanthanide rare earth metal ions, including La 3+ Ce 3+ and Sm 3+ One or more of them.

[0015] Preferably, the concentration of the cation solution is 0.2 to 1.0 mol / L, and the mass ratio of the SAPO-56 zeolite molecular sieve to the volume of the cation solution is 1 g: (40 to 80) mL.

[0016] Preferably, the ion exchange temperature is 40–80°C and the time is 3–8 h; the calcination temperature is 400–800°C and the time is 3–10 h.

[0017] The present invention provides a modified SAPO-56 zeolite molecular sieve prepared by the preparation method described above, wherein the modified SAPO-56 zeolite molecular sieve is an alkali metal ion modified SAPO-56 zeolite molecular sieve or a lanthanide rare earth metal ion modified SAPO-56 zeolite molecular sieve.

[0018] This invention provides the application of the modified SAPO-56 zeolite molecular sieve described above in the selective adsorption of carbon dioxide.

[0019] Preferably, the selective adsorption includes selectively adsorbing carbon dioxide from a mixture of nitrogen and carbon dioxide.

[0020] This invention provides a method for preparing modified SAPO-56 zeolite molecular sieves, comprising the following steps: mixing a silicon source, an aluminum source, phosphoric acid, a template agent, and water to obtain an initial reaction gel; wherein the template agent is N,N,N',N'-tetramethyl-1,6-hexanediamine; crystallizing the initial reaction gel to obtain a SAPO-56 zeolite molecular sieve, wherein the SAPO-56 zeolite molecular sieve contains the template agent; mixing the SAPO-56 zeolite molecular sieve with a cation solution for ion exchange; calcining the resulting ion exchange product to obtain a modified SAPO-56 zeolite molecular sieve; wherein the cations in the cation solution include alkali metal ions or lanthanide rare earth metal ions. In existing technologies, the modification of molecular sieves typically involves removing the template agent before ion exchange. This method can easily lead to the collapse of the molecular sieve framework. This invention, for the first time, involves ion exchange of SAPO-56 zeolite molecular sieve before removing the template agent. The SAPO-56 after metal cation exchange maintains excellent crystal structure stability, resulting in a high degree of crystallinity in the modified SAPO-56 zeolite molecular sieve, which in turn maintains stable strength and adsorption performance in gas adsorption. This invention uses alkali metal ions or lanthanide rare earth metal ions to perform ion exchange on SAPO-56 zeolite molecular sieve. Alkali metal ions or lanthanide rare earth metal ions replace hydrogen ions as the balancing charge, thereby increasing the internal electric field strength of the zeolite. Compared with the original SAPO-56 molecular sieve powder, the adsorption performance for CO2 with high polarizability is significantly improved, exhibiting excellent CO2 / N2 gas adsorption and separation performance.

[0021] The results of the examples show that when the cation is an alkali metal ion, the prepared modified SAPO-56 zeolite molecular sieve has a saturated adsorption capacity of 0.45–3.83 mmol / g (1 bar, 298 K) for CO2 at 298 K, and a CO2-N2 separation coefficient of 88–1594 (0.15 bar / 0.85 bar, 298 K); when the cation is a lanthanide rare earth metal ion, the prepared modified SAPO-56 zeolite molecular sieve has a saturated adsorption capacity of 3.56–4.30 mmol / g (1 bar, 298 K) for CO2, and a CO2-N2 separation coefficient of 894–994 (0.15 bar / 0.85 bar, 298 K). Attached Figure Description

[0022] Figure 1M-SAPO-56 (M = Li) prepared in Example 1 + Na + K + Cs + The molecular sieve of type 1 and the M-SAPO-56-C (M=Li) prepared in Comparative Example 1 + Na + K + Cs + XRD pattern of )

[0023] Figure 2 This is a SEM image of the M-SAPO-56 molecular sieve prepared in Example 1. Figure 2 In the middle (a) to (d), they correspond to Li-SAPO-56, Na-SAPO-56, K-SAPO-56, and Cs-SAPO-56, respectively;

[0024] Figure 3 Ln-SAPO-56 (Ln = La) prepared in Example 2 3+ Ce 3+ Sm 3+ The Ln-SAPO-56-C (Ln=La) type zeolite molecular sieve prepared in Comparative Example 2 and the Ln-SAPO-56-C (Ln=La) type zeolite molecular sieve prepared in Comparative Example 2 3+ Ce 3+ Sm 3+ XRD pattern of )

[0025] Figure 4 This is a SEM image of the Ln-SAPO-56 zeolite molecular sieve prepared in Example 2. Figure 4 In the middle, (a) to (c) correspond to Sm-SAPO-56, La-SAPO-56, and Ce-SAPO-56, respectively;

[0026] Figure 5 M-SAPO-56 (M = Li) prepared in Example 1 + Na + K + Cs + CO2 adsorption isotherm at 298 K;

[0027] Figure 6 M-SAPO-56 (M = Li) prepared in Example 1 + Na + K + Cs + The N2 adsorption isotherm at 298 K;

[0028] Figure 7 Ln-SAPO-56 (Ln-=La) prepared in Example 2 3+ Ce3+ Sm 3+ CO2 adsorption isotherm at 298 K;

[0029] Figure 8 Ln-SAPO-56 (Ln = La) prepared in Example 2 3+ Ce 3+ Sm 3+ The N2 adsorption isotherm at 298 K. Detailed Implementation

[0030] This invention provides a method for preparing modified SAPO-56 zeolite molecular sieves, comprising the following steps:

[0031] A silicon source, an aluminum source, phosphoric acid, a template agent, and water were mixed to obtain an initial reaction gel; the template agent was N,N,N',N'-tetramethyl-1,6-hexanediamine.

[0032] The initial reaction gel was crystallized to obtain SAPO-56 zeolite molecular sieve, which contains a template agent.

[0033] The SAPO-56 zeolite molecular sieve is mixed with a cation solution for ion exchange, and the resulting ion exchange product is calcined to obtain a modified SAPO-56 zeolite molecular sieve; the cations in the cation solution include alkali metal ions or lanthanide rare earth metal ions.

[0034] Unless otherwise specified, all raw materials involved in this invention are commercially available products well known to those skilled in the art.

[0035] This invention mixes a silicon source, an aluminum source, phosphoric acid, a template agent, and water to obtain an initial reaction gel. In this invention, the template agent is N,N,N',N'-tetramethyl-1,6-hexanediamine. In this invention, the silicon source preferably includes one or more of silica sol, sodium silicate, potassium silicate, and silica fume, more preferably silica sol or sodium silicate, wherein the silica content in the silica sol is preferably 20-40 wt%, more preferably 40 wt%. In this invention, the aluminum source preferably includes one or more of aluminum hydroxide, aluminum oxide, aluminum chloride, aluminum sulfate, sodium aluminate, boehmite, aluminum isopropoxide, and gibbsite, more preferably aluminum chloride, sodium aluminate, boehmite, or aluminum isopropoxide. In this invention, the phosphoric acid is preferably added in the form of an aqueous phosphoric acid solution, wherein the mass fraction of the aqueous phosphoric acid solution is preferably 85%.

[0036] In this invention, the silicon source, aluminum source, and phosphoric acid are calculated as SiO2, Al2O3, and P2O5, respectively. The molar ratio of the silicon source, aluminum source, phosphoric acid, template agent, and water is preferably (0.2-1):(0.5-1):0.37:(2-3):(20-100), more preferably (0.2-0.8):(0.5-0.7):0.37:(2-2.7):(40-100), and even more preferably (0.5-0.8):(0.5-0.7):0.37:(2-2.7):(40-80).

[0037] In this invention, the mixing of the silicon source, aluminum source, phosphoric acid, template agent, and water preferably includes the following steps:

[0038] Water and phosphoric acid are mixed in the first step to obtain the first mixed system;

[0039] The first mixture system and the aluminum source are mixed a second time to obtain a second mixture system;

[0040] The second mixture and the silicon source are then mixed a third time to obtain the third mixture.

[0041] The third mixing system and the template agent are mixed in a fourth step to obtain the initial reaction gel.

[0042] In this invention, phosphoric acid is preferably added to water for the first mixing. The time for this first mixing is not specifically limited, as long as the raw materials are mixed evenly. In this invention, an aluminum source is preferably added to the first mixing system for the second mixing, and the second mixing time is preferably 1 hour. In this invention, a silicon source is preferably added to the second mixing system for the third mixing, and the third mixing time is preferably 2 hours. In this invention, the first, second, and third mixing methods are all preferably stirred. In this invention, the template agent is preferably added dropwise to the third mixing system. Initially, the mixed solution is flocculent when the template agent is added, and the next drop is added only after the flocculent material gradually becomes a transparent solution. After the template agent is completely added, the resulting mixed system is preferably stirred for 24 hours to obtain an initial reaction gel.

[0043] After obtaining the initial reactive gel, the present invention crystallizes the initial reactive gel to obtain a SAPO-56 zeolite molecular sieve, wherein the SAPO-56 zeolite molecular sieve contains a template agent. In the present invention, the crystallization temperature is preferably 150–220°C, more preferably 160–210°C, and even more preferably 190–200°C; the crystallization time is preferably 2–6 days, more preferably 3–6 days, and even more preferably 4–5 days. In the present invention, the crystallization method is preferably static crystallization. In embodiments of the present invention, the static crystallization is preferably carried out in a high-pressure reactor.

[0044] After crystallization, the present invention preferably performs solid-liquid separation on the crystallized system, and dries the resulting solid material to obtain SAPO-56 zeolite molecular sieve, wherein the SAPO-56 molecular sieve contains a template agent. The present invention does not specifically limit the method of solid-liquid separation; any solid-liquid separation method well known in the art can be used, such as vacuum filtration or centrifugation. The present invention also does not specifically limit the drying method; any drying method well known to those skilled in the art can be used. In the embodiments of the present invention, the drying method is preferably oven drying, the drying temperature is preferably 70–130°C, more preferably 80°C, and the drying time is preferably 12 hours.

[0045] After obtaining the SAPO-56 zeolite molecular sieve, this invention mixes the SAPO-56 zeolite molecular sieve with a cation exchange solution for ion exchange, and then calcines the resulting ion exchange product to obtain a modified SAPO-56 zeolite molecular sieve. This invention performs ion exchange on the molecular sieve without removing the template agent. In this invention, the cations in the cation solution include alkali metal ions or lanthanide rare earth metal ions, and the alkali metal ions preferably include Li... + Na + K + and Cs + One or more of the lanthanides, wherein the lanthanide rare earth metal ions preferably include La. 3+ Ce 3+ and Sm 3+ One or more of the following. In this invention, the cations in the cation solution are preferably derived from soluble alkali metal salts or soluble lanthanum salts. The soluble alkali metal salts are preferably alkali metal chlorides or alkali metal nitrates, such as lithium chloride, lithium nitrate, sodium chloride, sodium nitrate, potassium chloride, potassium nitrate, cesium chloride, and cesium nitrate. The soluble rare earth salts are preferably lanthanum chlorides or lanthanum nitrates, such as lanthanum chloride, lanthanum nitrate, cerium chloride, cerium nitrate, samarium chloride, and samarium nitrate.

[0046] In this invention, the concentration of the cation solution is preferably 0.2-1.0 mol / L, more preferably 0.25-0.5 mol / L; the ratio of the mass of the SAPO-56 zeolite molecular sieve to the volume of the cation solution (i.e., the solid-liquid ratio S / L) is preferably 1 g:(40-80) mL, more preferably 1 g:(40-60) mL.

[0047] In this invention, the preferred temperature for the ion exchange reaction is 40–80°C, more preferably 40–60°C; the preferred time is 3–8 h, more preferably 4–7 h. During the ion exchange reaction, the cations exchange ions with the SAPO-56 zeolite molecular sieve, altering the cation composition and internal electric field strength of the SAPO-56 zeolite molecular sieve, thereby significantly improving the selective adsorption capacity of the modified SAPO-56 for CO2.

[0048] After the ion exchange, the present invention preferably performs solid-liquid separation on the resulting system, and washes and dries the resulting solid material to obtain the ion exchange product. In the present invention, the number of water washings is preferably three times, and the purpose of water washing is to remove impurities remaining on the sample surface; the drying temperature is preferably 80°C, and the drying time is preferably 12 hours.

[0049] In this invention, the calcination temperature is preferably 400–800°C, more preferably 550–700°C; the calcination time is preferably 3–10 h, more preferably 4–7 h. In this invention, the calcination atmosphere is preferably air, and the calcination is preferably carried out in a muffle furnace. In this invention, the purpose of the calcination is to remove the template agent N,N,N',N'-tetramethyl-1,6-hexanediamine. In the prior art, molecular sieve modification usually involves removing the template agent first and then performing ion exchange. This method easily causes the collapse of the molecular sieve framework structure. This invention is the first to perform ion exchange on SAPO-56 type zeolite molecular sieves before calcination to remove the template agent. SAPO-56 after metal cation exchange maintains excellent crystal structure stability.

[0050] This invention provides a modified SAPO-56 zeolite molecular sieve prepared by the preparation method described above. The modified SAPO-56 zeolite molecular sieve is either alkali metal ion modified SAPO-56 or lanthanide rare earth metal ion modified SAPO-56. In embodiments of this invention, the alkali metal ion modified SAPO-56 and lanthanide rare earth metal ion modified SAPO-56 zeolite molecular sieves are named M-SAPO-56 and Ln-SAPO-56, respectively. The modified SAPO-56 zeolite molecular sieve provided by this invention maintains good crystallinity and morphology.

[0051] This invention provides the application of the modified SAPO-56 zeolite molecular sieve described above in the selective adsorption of carbon dioxide, that is, the modified SAPO-56 zeolite molecular sieve can be used as a selective adsorbent for carbon dioxide. In this invention, the selective adsorption preferably includes the selective adsorption of carbon dioxide from a mixed gas containing nitrogen and carbon dioxide (CO2 / N2 = 15 / 85), wherein the mixed gas of nitrogen and carbon dioxide preferably comes from flue gas, and the volume ratio of carbon dioxide to nitrogen in the mixed gas is preferably 15:85.

[0052] In this invention, before application, the modified SAPO-56 zeolite molecular sieve is preferably activated under vacuum conditions; the activation temperature is preferably 200–450°C, more preferably 300–350°C, and the activation time is preferably 8–12 hours, more preferably 9–10 hours. This invention removes moisture from the molecular sieve through activation.

[0053] In this invention, on the one hand, the kinetic diameter of CO2 (0.33 nm) is smaller than that of CH4 (0.38 nm) and N2 (0.364 nm); on the other hand, the polarizability of CO2 is much greater than that of N2. The modified SAPO-56 zeolite molecular sieve, because alkali metal ions or lanthanide rare earth metal ions replace hydrogen ions as the balancing charge, results in a stronger electric field within the zeolite. Compared to raw SAPO-56 molecular sieve powder, the modified SAPO-56 molecular sieve exhibits significantly improved adsorption performance for CO2 with high polarizability, demonstrating excellent CO2 / N2 gas adsorption and separation performance.

[0054] To further illustrate the present invention, the modified SAPO-56 zeolite molecular sieve, its preparation method, and its application are described in detail below with reference to examples, but these should not be construed as limiting the scope of protection of the present invention.

[0055] Example 1

[0056] Modified M-SAPO-56 (M = Li + Na + K + Cs + The preparation method of type () zeolite molecular sieve is as follows:

[0057] (1) Add 2.30g of phosphoric acid aqueous solution (85wt%) to 27.868g of deionized water and stir. Then add 2.652g of sodium aluminate to the beaker and stir for 1h. Add 2.023g of silica sol (SiO2 content 40wt%) and stir evenly for 2h. Then add 11.459g of organic template agent N,N,N',N'-tetramethyl-1,6-hexanediamine dropwise. When the template agent is first added, the mixed solution in the beaker is flocculent. Wait until the flocculent gradually becomes a transparent solution before adding the next drop. After all the template agent is added, cover the final mixed solution with a sealing film and stir at room temperature for 24h to obtain the initial reaction gel.

[0058] The initial reaction gel was transferred into a high-pressure reactor and crystallized at 200°C for 4 days. Then it was filtered, and the resulting solid material was dried at 80°C for 12 hours to obtain SAPO-56 type zeolite molecular sieve.

[0059] (2) The SAPO-56 zeolite molecular sieve prepared in Example 1 was mixed with 0.5 mol / L LiCl, NaCl, KCl and CsCl solutions at 60°C for 4 h according to the ratio of the mass of SAPO-56 zeolite molecular sieve to the volume of alkali metal chloride solution S / L = 1 g: 50 mL. After stirring, the mixture was filtered, and the resulting solid material was washed with deionized water and dried at 80°C for 12 h to obtain the ion exchange product.

[0060] (3) The ion exchange product was placed in a muffle furnace and calcined at 550°C for 6 hours to obtain a modified SAPO-56 type zeolite molecular sieve, denoted as M-SAPO-56 (M = Li + Na + K + Cs + () type zeolite molecular sieve.

[0061] Comparative Example 1

[0062] M-SAPO-56-C(M=Li + Na + K + Cs + The preparation method of type () zeolite molecular sieve is as follows:

[0063] (1) The preparation of SAPO-56 type zeolite molecular sieve is the same as in Example 1;

[0064] (2) The SAPO-56 zeolite molecular sieve obtained in step (1) is placed in a muffle furnace and calcined at 550°C for 6 hours to obtain H-SAPO-56 zeolite molecular sieve.

[0065] (3) After ion exchange of H-SAPO-56 molecular sieve according to the exchange method in step (2) of Example 1, calcination is carried out according to the calcination method in step (3) of Example 1 to obtain M-SAPO-56-C (M = Li + Na + K + Cs + () type zeolite molecular sieve.

[0066] Figure 1 To implement 1, M(Li) was prepared. + Na + K + Cs + SAPO-56 molecular sieve and M(Li) prepared in Comparative Example 1 + Na + K + Cs + XRD pattern of SAPO-56-C molecular sieve. Alkali metal ions (Li) + Na + K + Cs + After adopting the method of first exchanging and then calcining, the M-SAPO-56 molecular sieve still maintains its original topological structure, and its crystallinity is similar to that of the calcined and then exchanged sample M-SAPO-56-C (M = Li + Na + K + Cs + (Compared to Example 1) it remains at a high level.

[0067] Figure 2 M(Li) prepared in Example 1 + Na + K + Cs + SEM image of SAPO-56 molecular sieve. Figure 2 In the middle (a) to (d), they correspond to Li-SAPO-56, Na-SAPO-56, K-SAPO-56, and Cs-SAPO-56, respectively. From Figure 2 It can be seen that the M(Li) prepared in Example 1 + Na + K + Cs + The SAPO-56 molecular sieve has a hexagonal "cake" shape and no amorphous form exists.

[0068] Example 2

[0069] Ln-SAPO-56(Ln=La 3+ Ce3+ Sm 3+ The preparation method of type () zeolite molecular sieve is as follows:

[0070] (1) The preparation of SAPO-56 type zeolite molecular sieve is the same as in Example 1.

[0071] (2) The SAPO-56 zeolite molecular sieve prepared in step (1) was mixed with a 0.25 mol / L rare earth metal nitrate solution at a mass ratio of S / L = 1 g: 50 mL. 3+ Ce 3+ Sm 3+ After stirring and mixing at 60℃ for 4 hours, the mixture was filtered. The resulting solid material was washed with deionized water and dried at 80℃ for 12 hours to obtain the ion exchange product.

[0072] (3) The ion exchange product was placed in a muffle furnace and calcined at 550°C for 6 hours to obtain a modified SAPO-56 type zeolite molecular sieve, denoted as Ln-SAPO-56 (Ln = La). 3+ Ce 3+ Sm 3+ () type zeolite molecular sieve.

[0073] Comparative Example 2

[0074] Ln-SAPO-56-C(Ln=La 3+ Ce 3+ Sm 3+ The preparation method of type () zeolite molecular sieve is as follows:

[0075] (1) The preparation of SAPO-56 type zeolite molecular sieve is the same as in Example 1.

[0076] (2) The SAPO-56 zeolite molecular sieve obtained in step (1) is placed in a muffle furnace and calcined at 550°C for 6 hours to obtain H-SAPO-56 zeolite molecular sieve.

[0077] (3) After ion exchange of H-SAPO-56 molecular sieve according to the exchange method in step (2) of Example 2, calcination is carried out according to the calcination method in step (3) to obtain Ln-SAPO-56-C (Ln = La). 3+ Ce 3+ Sm 3+ () type zeolite molecular sieve.

[0078] Figure 3 Ln-SAPO-56 (Ln = La) prepared in Example 2 3+ Ce 3+ Sm 3+The XRD pattern of the α-type zeolite molecular sieve shows that rare earth lanthanide metal ions (La) can be observed. 3+ Ce 3+ Sm 3+ After the exchange, the SAPO-56 molecular sieve retains its original topology. Rare earth lanthanide metal ions (La...) 3+ Ce 3+ Sm 3+ After adopting the method of first exchanging and then roasting, Ln-SAPO-56 (Ln=La) 3+ Ce 3+ Sm 3+ The molecular sieve retains its original topology, and its crystallinity is similar to that of the calcined and re-exchanged sample Ln-SAPO-56-C (Ln = La). 3+ Ce 3+ Sm 3+ (Compared to Example 2) it remains at a high level.

[0079] Figure 4 This is a SEM image of the Ln-SAPO-56 zeolite molecular sieve prepared in Example 2. Figure 4 In the diagram, (a) to (c) correspond to Sm-SAPO-16, La-SAPO-56, and Ce-SAPO-56, respectively. (From...) Figure 4 It can be seen that the Ln-SAPO-56 (Ln=La) prepared in Example 2 3+ Ce 3+ Sm 3+ The molecular sieve has a hexagonal "cake" shape and no amorphous form exists.

[0080] Application examples

[0081] Gas selective adsorption and separation tests were conducted using the modified SAPO-56 molecular sieves prepared in Examples 1 and 2 as raw materials. Before the test, all zeolite molecular sieves were activated at 350℃ under vacuum for 10 hours. After the samples cooled to room temperature, single-component gas isothermal adsorption-desorption tests were performed at a temperature of 298K and a pressure of 0–1 bar. The test results are as follows:

[0082] Figure 5 M-SAPO-56 (M = Li) prepared in Example 1 + Na + K + Cs + CO2 adsorption isotherm at 298K.

[0083] Figure 6 M-SAPO-56 (M = Li) prepared in Example 1 + Na + K+ Cs + The N2 adsorption isotherm at 298 K.

[0084] Figure 7 The Ln-SAPO-56 (Ln = La) prepared in Example 2 3+ Ce 3+ Sm 3+ CO2 adsorption isotherm at 298 K.

[0085] Figure 8 The Ln-SAPO-56 (Ln = La) prepared in Example 2 3+ Ce 3+ Sm 3+ The N2 adsorption isotherm at 298 K.

[0086] Table 1 lists the M-SAPO-56 (M = Li) prepared in Examples 1 and 2. + Na + K + Cs + ) and Ln-SAPO-56 (Ln=La 3 + Ce 3+ Sm 3+ The separation effect of type zeolite molecular sieve.

[0087] Table 1 M-SAPO-56 (M = Li) + Na + K + Cs + Type ) and Ln-SAPO-56 (Ln=La 3+ Ce 3+ Sm 3+ Gas separation effect of type zeolite molecular sieve

[0088]

[0089]

[0090] As shown in Table 1, compared to the unmodified SAPO-56 zeolite molecular sieve, the M-SAPO-56 (M=Li) obtained after ion exchange modification... + Na + K + Cs + ) type zeolite molecular sieves and Ln-SAPO-56 (Ln=La) 3+ Ce 3+ Sm 3+ The selective adsorption performance of CO2 by the () type zeolite molecular sieve is significantly improved.

[0091] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing modified SAPO-56 type zeolite molecular sieve, characterized in that, Includes the following steps: A silicon source, an aluminum source, phosphoric acid, a template agent, and water are mixed to obtain an initial reaction gel; the template agent is N,N,N',N'-tetramethyl-1,6-hexanediamine; the silicon source, aluminum source, and phosphoric acid are calculated as SiO2, Al2O3, and P2O5, respectively, and the molar ratio of the silicon source, aluminum source, phosphoric acid, template agent, and water is (0.2-1):(0.5-1):0.37:(2-3):(20-100); The initial reaction gel was crystallized to obtain SAPO-56 zeolite molecular sieve, which contains a template agent. The SAPO-56 zeolite molecular sieve was mixed with a cation exchange solution for ion exchange, and the resulting ion exchange product was calcined to obtain a modified SAPO-56 zeolite molecular sieve. The cations in the cation solution included alkali metal ions or lanthanide rare earth metal ions, wherein the alkali metal ion was Li. + Na + and K + One or more of the lanthanide rare earth metal ions, wherein the lanthanide rare earth metal ion is La 3+ Ce 3+ and Sm 3+ One or more of them.

2. The preparation method according to claim 1, characterized in that, The silicon source includes one or more of silica sol, sodium silicate, potassium silicate, and silica; the aluminum source includes one or more of aluminum hydroxide, aluminum oxide, aluminum chloride, aluminum sulfate, sodium aluminate, boehmite, aluminum isopropoxide, and gibbsite.

3. The preparation method according to claim 1, characterized in that, The crystallization temperature is 150–220°C, and the time is 2–6 days.

4. The preparation method according to claim 1, characterized in that, The concentration of the cation solution is 0.2–1.0 mol / L, and the mass ratio of the SAPO-56 zeolite molecular sieve to the volume of the cation solution is 1 g: (40–80) mL.

5. The preparation method according to claim 1, characterized in that, The ion exchange temperature is 40–80°C and the time is 3–8 h; the calcination temperature is 400–800°C and the time is 3–10 h.

6. The modified SAPO-56 zeolite molecular sieve prepared by the preparation method according to any one of claims 1 to 5, wherein the modified SAPO-56 zeolite molecular sieve is an alkali metal ion modified SAPO-56 zeolite molecular sieve or a lanthanide rare earth metal ion modified SAPO-56 zeolite molecular sieve.

7. The application of the modified SAPO-56 zeolite molecular sieve according to claim 6 in the selective adsorption of carbon dioxide.

8. The application according to claim 7, characterized in that, The selective adsorption includes selectively adsorbing carbon dioxide from a mixture of nitrogen and carbon dioxide.

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