Synthesis and CO2 Adsorption and Separation Application of a Modified SSZ-16 Zeolite Molecular Sieves

Abstract

This invention provides a method for synthesizing and applying modified SSZ-16 zeolite molecular sieve to CO2 adsorption and separation, relating to the field of chemical adsorbent technology. The invention involves mixing a silicon source, an aluminum source, an alkali source, a template agent, and water; crystallizing the resulting initial reaction gel and calcining it, then mixing it with an ammonium chloride solution for ion exchange; and then reacting the resulting ammonium-type SSZ-16 zeolite molecular sieve with a metal cation solution (Li). + Na + K + After ion exchange, the mixture is calcined to obtain modified SSZ-16 zeolite molecular sieve. This invention applies modified SSZ-16 zeolite molecular sieve to the field of selective CO2 adsorption and separation for the first time. The resulting modified SSZ-16 zeolite molecular sieve exhibits excellent CO2 / N2 and CO2 / CH4 gas adsorption and separation performance. In addition, this modified zeolite molecular sieve has the advantages of easy regeneration and excellent structural stability, and has better application prospects compared with other adsorbents.

Description

Technical Field

[0001] This invention relates to the field of chemical adsorbent technology, and in particular to the synthesis and CO2 adsorption and separation application of a modified SSZ-16 zeolite molecular sieve. Background Technology

[0002] SSZ-16 small-pore molecular sieves with an AFX-type framework are widely used in methanol-to-olefins (MTO) and denitrification (DeNOx) processes due to their suitable pore volume, large specific surface area, and excellent hydrothermal stability. x Catalysis and other fields.

[0003] Stacey I. Zones et al. (SIUS Patent 4,508,837, 1985) first synthesized SSZ-16 molecular sieves via a hydrothermal reaction using 1,4-bis(1-azoniabicyclo[2.2.2]octane)butyl dibromide as an organic template, aluminum sulfate as the aluminum source, and sodium silicate as the silicon source. Since the first synthesis of SSZ-16 zeolite molecular sieves in 1985, research on their applications has focused entirely on MTO and DeNOx. x In the field of catalysis, no researchers have applied the modified SSZ-16 zeolite molecular sieve to the field of gas adsorption and separation.

[0004] In 2016, David S. Sholl and Ryan P. Lively (Nature, 532, 435-437, 2016) listed the adsorption and separation technology of low-concentration greenhouse gases in emissions as one of the seven gas adsorption and separation technologies that could change the world. Carbon dioxide is a typical example of a greenhouse gas. Since the Industrial Revolution, the concentration of carbon dioxide in the atmosphere has been increasing. This continuously rising concentration of carbon dioxide will lead to a series of climate risks, including global warming. 40% to 60% of carbon dioxide emissions come from flue gas emissions after the combustion of fossil fuels. Industrially, liquid amine solutions are mainly used to adsorb and separate carbon dioxide from flue gas. However, the regeneration of liquid amine solutions requires a large amount of energy, and their alkalinity can cause a certain degree of corrosion to equipment, greatly increasing industrial costs. Furthermore, liquid amine solutions are unstable and subject to oxidative degradation. Summary of the Invention

[0005] In view of this, the purpose of this invention is to provide a method for synthesizing and applying a modified SSZ-16 zeolite molecular sieve to CO2 adsorption and separation. The modified SSZ-16 zeolite molecular sieve prepared by this invention exhibits excellent selective adsorption and separation performance of carbon dioxide, and is easily regenerated, has excellent structural stability, and is non-corrosive.

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

[0007] This invention provides a method for preparing modified SSZ-16 zeolite molecular sieve, comprising the following steps:

[0008] The silicon source, aluminum source, alkali source, template agent and water are mixed to obtain the initial reaction gel;

[0009] The initial reactive gel was crystallized to obtain SSZ-16 zeolite molecular sieve.

[0010] After the SSZ-16 zeolite molecular sieve is first calcined, it is mixed with ammonium chloride solution for first ion exchange to obtain ammonium-type SSZ-16 zeolite molecular sieve.

[0011] The ammonium-type SSZ-16 zeolite molecular sieve is mixed with a metal cation solution for a second ion exchange, followed by a second calcination to obtain the modified SSZ-16 zeolite molecular sieve; the cations in the metal cation solution include Li. + Na + and K + One or more of them.

[0012] Preferably, the silicon source includes one or more of LTA zeolite, FAU zeolite, MFI zeolite, silica sol, tetraethyl orthosilicate, sodium silicate, and silica.

[0013] The aluminum source includes one or more of aluminum hydroxide, aluminum oxide, aluminum chloride, aluminum sulfate, sodium aluminate, boehmite, FAU zeolite, LTA zeolite, and MFI zeolite.

[0014] The alkaline source includes hydroxides;

[0015] The template agent includes Et6-diquat-n dibromide and / or DABCO2-diquat-m dibromide, where n = 2 to 10, m = 2 to 10, and m and n are both integers.

[0016] Preferably, the silicon source and aluminum source are calculated as SiO2 and Al2O3, respectively, and the molar ratio of the template agent, silicon source, aluminum source, alkali source and water is (0.5-7):(3-80):1:(5-100):(200-1000).

[0017] Preferably, the crystallization temperature is 110–220°C and the time is 1–10 days.

[0018] Preferably, the first calcination temperature is 400–600°C and the time is 5–10 h; the second calcination temperature is 400–800°C and the time is 3–8 h.

[0019] Preferably, the concentration of the ammonium chloride solution is 0.05–10 mol / L, the temperature of the first ion exchange is 20–100°C, and the time is 2–24 h.

[0020] Preferably, the concentration of the metal cation solution is 0.01–10 mol / L, the temperature of the second ion exchange is 20–100 °C, and the time is 2–24 h.

[0021] This invention provides a modified SSZ-16 zeolite molecular sieve prepared by the preparation method described above; the modified SSZ-16 zeolite molecular sieve is a metal cation exchange SSZ-16 zeolite molecular sieve, wherein the metal cation includes Li + Na + and K + One or more of them.

[0022] This invention provides the application of the modified SSZ-16 zeolite molecular sieve described above in the selective adsorption and separation of carbon dioxide in mixed gases.

[0023] Preferably, the mixed gas also includes nitrogen and / or methane.

[0024] This invention provides a method for preparing modified SSZ-16 zeolite molecular sieve, comprising the following steps: mixing a silicon source, an aluminum source, an alkali source, a template agent, and water to obtain an initial reaction gel; crystallizing the initial reaction gel to obtain an SSZ-16 zeolite molecular sieve; subjecting the SSZ-16 zeolite molecular sieve to a first calcination, then mixing it with an ammonium chloride solution for a first ion exchange to obtain an ammonium-type SSZ-16 zeolite molecular sieve; mixing the ammonium-type SSZ-16 zeolite molecular sieve with a metal cation solution for a second ion exchange, followed by a second calcination to obtain the modified SSZ-16 zeolite molecular sieve; wherein the cation in the metal cation solution includes Li + Na + and K + One or more of the following. This invention involves calcining SSZ-16 zeolite molecular sieve to remove the template agent, followed by ion exchange, wherein Li... + Na + K +Ion exchange with cations can alter the cation composition and internal electric field strength of SSZ-16 zeolite molecular sieves, thereby significantly improving the selective adsorption capacity of modified SSZ-16 for CO2. This invention modifies SSZ-16 zeolite molecular sieves and applies it for the first time to the field of selective carbon dioxide adsorption and separation. The resulting modified SSZ-16 zeolite molecular sieve exhibits excellent CO2 / N2 and CO2 / CH4 gas adsorption and separation performance. Furthermore, the modified SSZ-16 zeolite molecular sieve is easily regenerated, has excellent structural stability, and is non-corrosive. The modified SSZ-16 zeolite molecular sieve prepared by this invention shows better application prospects in the field of carbon dioxide adsorption and separation compared to other adsorbents. Attached Figure Description

[0025] Figure 1 XRD patterns of the modified SSZ-16 zeolite molecular sieves prepared in Examples 1-4, Cs-SSZ-16-DABCO of Comparative Example 1, and unmodified H-SSZ-16-DABCO zeolite molecular sieve of Comparative Example 2.

[0026] Figure 2 SEM images of the modified SSZ-16 zeolite molecular sieves prepared in Examples 1-4, Cs-SSZ-16-DABCO of Comparative Example 1, and unmodified H-SSZ-16-DABCO zeolite molecular sieves of Comparative Example 2.

[0027] Figure 3 CO2 adsorption isotherms at 298 K for the modified SSZ-16 zeolite molecular sieves prepared in Examples 1-4, Cs-SSZ-16-DABCO of Comparative Example 1, and unmodified H-SSZ-16-DABCO zeolite molecular sieves of Comparative Example 2.

[0028] Figure 4 CH4 adsorption isotherms at 298 K for the modified SSZ-16 zeolite molecular sieves prepared in Examples 1-4, the Cs-SSZ-16-DABCO zeolite molecular sieve of Comparative Example 1, and the unmodified H-SSZ-16-DABCO zeolite molecular sieve of Comparative Example 2.

[0029] Figure 5 The N2 adsorption isotherms at 298 K for the modified SSZ-16 zeolite molecular sieves prepared in Examples 1-4, the Cs-SSZ-16-DABCO zeolite molecular sieve of Comparative Example 1, and the unmodified H-SSZ-16-DABCO zeolite molecular sieve of Comparative Example 2. Detailed Implementation

[0030] This invention provides a method for preparing modified SSZ-16 zeolite molecular sieve, comprising the following steps:

[0031] The silicon source, aluminum source, alkali source, template agent and water are mixed to obtain the initial reaction gel;

[0032] The initial reactive gel was crystallized to obtain SSZ-16 zeolite molecular sieve.

[0033] After the SSZ-16 zeolite molecular sieve is first calcined, it is mixed with ammonium chloride solution for first ion exchange to obtain ammonium-type SSZ-16 zeolite molecular sieve.

[0034] The ammonium-type SSZ-16 zeolite molecular sieve is mixed with a metal cation solution for a second ion exchange, followed by a second calcination to obtain the modified SSZ-16 zeolite molecular sieve; the cations in the metal cation solution include Li. + Na + and K + One or more of them.

[0035] Unless otherwise specified, all raw materials involved in this invention are commercially available products well known to those skilled in the art.

[0036] This invention mixes a silicon source, an aluminum source, an alkali source, a template agent, and water to obtain an initial reaction gel. In this invention, the silicon source preferably includes one or more of LTA zeolite, FAU zeolite, MFI zeolite, silica sol, tetraethyl orthosilicate (TEOS), sodium silicate, and silica, more preferably one or more of LTA zeolite, FAU zeolite, MFI zeolite, and silica sol. The silica sol preferably contains 20-40 wt% silica, more preferably 30 wt%. In this invention, the aluminum source preferably includes one or more of aluminum hydroxide, alumina, aluminum chloride, aluminum sulfate, sodium aluminate, boehmite, FAU zeolite, LTA zeolite, and MFI zeolite, more preferably one or more of aluminum chloride, FAU zeolite, LTA zeolite, and MFI zeolite. In this invention, the alkali source preferably includes hydroxides, more preferably one or more of sodium hydroxide, potassium hydroxide, cesium hydroxide, and lithium hydroxide, more preferably potassium hydroxide.

[0037] In this invention, the template agent preferably comprises Et6-diquat-n dibromide and / or DABCO2-diquat-m dibromide, wherein n = 2 to 10, m = 2 to 10, and m and n are both integers. In the embodiments of this invention, n is preferably 4, and m is preferably 4. This invention does not have any particular requirements regarding the source of the template agent; it can be obtained from commercially available products or prepared using methods well-known to those skilled in the art.

[0038] In this invention, when the template agent is Et6-diquat-n dibromide, the template agent is preferably prepared by the following method:

[0039] Triethylamine was mixed with 1,n-dibromo-n-alkyl (n = 2–10, corresponding to the Chinese names ethyl, propane, butane, pentane, hexane, heptane, octane, nonane, and decane) and methanol at a molar ratio of 2:1:3. The mixture was stirred at room temperature for 24 hours. After the reaction was completed, the solid product was washed with diethyl ether and dried in an oven at 50°C for 12 hours to obtain the organic template agent Et6-diquat-n dibromide (1,n-dibromo-n-alkylethane dibromide, abbreviated as Et6-diquat-n, structure shown in Formula I, n = 2–10, corresponding to the Chinese names ethyl, propane, butane, pentane, hexane, heptane, octane, nonane, and decane).

[0040] In this invention, when the template agent is DABCO2-diquat-m dibromide, the template agent is preferably prepared by the following method:

[0041] 1,4-diazidobicyclo[2.2.2]octane (abbreviated as DABCO) was mixed with 1,m-dibromo-n-m-alkane (m = 2 to 10, corresponding to the Chinese names ethyl, propane, butane, pentane, hexane, heptane, octane, nonane, decane) and methanol at a molar ratio of 2:1:3. The mixture was stirred at room temperature for 24 hours. After the reaction was completed, the solid product was washed with diethyl ether and dried in an oven at 50°C for 12 hours to obtain the organic template agent DABCO2-diquat-m dibromide (1,m-bis(1,4-diazidobicyclo[2.2.2]octane)m-alkane dibromo derivative, abbreviated as DABCO2-diquat-m, with the structure shown in Formula II, m = 2 to 10, corresponding to the Chinese names ethyl, propane, butane, pentane, hexane, heptane, octane, nonane, decane).

[0042]

[0043] In this invention, the silicon source and aluminum source are calculated as SiO2 and Al2O3, respectively. The molar ratio of the template agent, silicon source, aluminum source, alkali source and water is preferably (0.5-7):(3-80):1:(5-100):(200-1000), more preferably (1-6):(8-56):1:(10-75):(250-1000), and even more preferably (1.2-5.5):(10-52):1:(10-56):(360-1000).

[0044] In this invention, the mixing of the silicon source, aluminum source, template agent, alkali source, and water preferably includes the following steps:

[0045] Water and template agent are mixed in the first step to obtain a first mixed system;

[0046] The first mixture, the aluminum source, and the silicon source are mixed a second time to obtain a second mixture.

[0047] The second mixture and the alkali source are mixed a third time to obtain the initial reaction gel.

[0048] In this invention, the first mixing time is preferably 2 hours; the second mixing time is preferably 1 day; and the third mixing time is determined by fully dissolving the alkali source. In this invention, the mixing method is preferably stirring.

[0049] After obtaining the initial reactive gel, the present invention crystallizes the initial reactive gel to obtain SSZ-16 zeolite molecular sieve (the SSZ-16 molecular sieve contains a template agent). In the present invention, the crystallization temperature is preferably 110-220℃, more preferably 140-210℃, and even more preferably 160-180℃; the crystallization time is preferably 1-10 days, more preferably 1-6 days, even more preferably 1-5 days, and most preferably 2-4 days. In the present invention, the crystallization method can be either static crystallization or dynamic crystallization; the crystallization is preferably carried out in a high-pressure reactor.

[0050] After crystallization, the present invention preferably performs solid-liquid separation on the resulting system, and dries the resulting solid material to obtain SSZ-16 zeolite molecular sieve. 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 80–100°C, and the drying time is preferably 12 hours.

[0051] After obtaining the SSZ-16 zeolite molecular sieve, the present invention subjectes the SSZ-16 zeolite molecular sieve to a first calcination, followed by a first ion exchange with an ammonium chloride solution to obtain an ammonium-type SSZ-16 zeolite molecular sieve. In this invention, the preferred temperature for the first calcination is 400–600°C, more preferably 500–550°C, and the preferred time is 5–10 h, more preferably 6–8 h; the first calcination removes the template agent. In this invention, the preferred concentration of the ammonium chloride solution is 0.05–10 mol / L, more preferably 0.1–5 mol / L, and the preferred mass ratio of the SSZ-16 zeolite molecular sieve to the volume of the ammonium chloride solution is 1–3 g: 40–150 mL, more preferably 1 g: 50–100 mL. In this invention, the preferred temperature for the first ion exchange is 20–100°C, more preferably 20–40°C, and the preferred time is 2–24 h, more preferably 3–10 h. In this embodiment of the invention, the first ion exchange is performed at room temperature. In this invention, the first ion exchange is preferably carried out under stirring conditions. By exchanging the calcined molecular sieve with an ammonium chloride solution, this invention facilitates the subsequent second ion exchange, resulting in a higher degree of metal cation exchange in the second ion exchange.

[0052] Following the first ion exchange, the resulting reaction solution is preferably subjected to sequential filtration, solid-phase washing, and drying to obtain ammonium-type SSZ-16 zeolite molecular sieve. In this invention, the washing is preferably done with water, and the drying temperature is preferably 100°C. The drying time is preferably 12 hours.

[0053] After obtaining the ammonium-type SSZ-16 zeolite molecular sieve, this invention mixes the ammonium-type SSZ-16 zeolite molecular sieve with a metal cation solution for a second ion exchange, followed by a second calcination to obtain the modified SSZ-16 zeolite molecular sieve. In this invention, the cations in the metal cation solution include Li. + Na + and K + One or more of the metal cations, preferably derived from the corresponding soluble metal salts, specifically, Li + Preferably derived from lithium chloride or lithium nitrate, Na + Preferred sources are sodium chloride or sodium nitrate, K +The cation is preferably derived from potassium chloride or potassium nitrate. In this invention, the concentration of the cation solution is preferably 0.01–10 mol / L, more preferably 0.1–5 mol / L; the mass ratio of the SSZ-16 zeolite molecular sieve to the volume of the cation solution (i.e., solid-liquid ratio S / L) is preferably 1 g:(10–200 mL), more preferably 1 g:(40–80) mL, and even more preferably 1 g:(50–60) mL. In this invention, the temperature of the second ion exchange is preferably 20–100 °C, more preferably 25–80 °C, and even more preferably 40–80 °C; the time is preferably 2–24 h, more preferably 3–8 h, and even more preferably 4–7 h. In this invention, the second ion exchange is preferably carried out under stirring conditions. This invention utilizes Li… + Na + K + Ion exchange with SSZ-16 zeolite molecular sieves by cations alters the cation composition and internal electric field strength of the SSZ-16 zeolite molecular sieve, thereby greatly improving the selective adsorption capacity of modified SSZ-16 for CO2.

[0054] After the second ion exchange, the resulting reaction solution is preferably subjected to filtration, solid-phase washing, and drying in sequence. In this invention, the washing is preferably water washing, and the drying temperature is preferably 100°C, and the drying time is preferably 12 hours.

[0055] In this invention, the preferred temperature for the second calcination is 400–800°C, more preferably 500–700°C, and the preferred time is 3–8 hours, more preferably 4–8 hours; the second calcination is preferably carried out in an air atmosphere. During the second calcination process, ammonium ions that have not been exchanged with the metal cations in the zeolite molecular sieve are removed, and the residual ammonium ions will volatilize in the form of ammonia.

[0056] This invention provides a modified SSZ-16 zeolite molecular sieve prepared by the preparation method described above. In this invention, the modified SSZ-16 zeolite molecular sieve is a metal cation exchange SSZ-16 zeolite molecular sieve, wherein the metal cation includes Li... + Na + and K + One or more of the following, and the modified SSZ-16 zeolite molecular sieve maintains good crystallinity and morphology. In the embodiments of the present invention, the modified SSZ-16 zeolite molecular sieve is represented as M-SSZ-16 (M = Li + Na + K + ).

[0057] This invention provides the application of the modified SSZ-16 zeolite molecular sieve described above in the selective adsorption and separation of carbon dioxide in a mixed gas, specifically, the modified SSZ-16 zeolite molecular sieve as a selective adsorbent for carbon dioxide. In this invention, the mixed gas preferably also includes nitrogen and / or methane. In embodiments of this invention, the modified SSZ-16 zeolite molecular sieve is preferably used as a selective adsorbent for carbon dioxide in a mixture of carbon dioxide and nitrogen (CO2-N2), and in a mixture of carbon dioxide and methane (CO2-CH4). In this invention, on 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 modified SSZ-16 type zeolite molecular sieve, because of alkali metal cations (Li... + Na + K + The presence of N2 causes partial blockage of the internal pores of the molecular sieve. There is a strong interaction between CO2 and metal cations, which causes the metal cations to move and allow CO2 to pass through. However, there is almost no interaction between N2 and alkali metal cations, so they cannot pass through. Therefore, efficient separation of CO2 in the CO2-N2 mixed system is achieved.

[0058] In this invention, the modified SSZ-16 zeolite molecular sieve is preferably activated before application. The activation preferably includes the following steps: activating the modified SSZ-16 zeolite molecular sieve under vacuum and at a temperature of 200–450°C. This invention does not have a specific limitation on the vacuum level; a vacuum level well-known in the art can be used. The activation time is preferably 8–12 hours.

[0059] To further illustrate the present invention, the synthesis and CO2 adsorption and separation application of the modified SSZ-16 zeolite molecular sieve provided by the present invention 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.

[0060] Example 1

[0061] Preparation of the organic template agent DABCO2-diquat-4dibromide:

[0062] 1,4-diazidobicyclo[2.2.2]octane (abbreviated as DABCO) was mixed with 1,4-dibromobutane and methanol at a molar ratio of 2:1:3 and stirred at room temperature for 24 hours. After the reaction was completed, the solid product was washed with diethyl ether and dried in an oven at 50°C for 12 hours to obtain the organic template agent DABCO2-diquat-4dibromide (1,4-bis(1,4-diazidobicyclo[2.2.2]octane)butane dibromo derivative, abbreviated as DABCO2-diquat-4).

[0063] Preparation of modified SSZ-16 zeolite molecular sieve:

[0064] Under stirring conditions at room temperature, 6.023 g of organic template agent DABCO2-diquat-4 was added to 43.15 mL of water and stirred until homogeneous. 8.759 g of MFI zeolite (Si / Al ratio Si / Al = 13.6) was added as both silicon and aluminum sources and stirred for 1 day. Then, 6.142 g of potassium hydroxide was slowly added and stirred to dissolve, resulting in a homogeneous initial reaction gel. The molar ratio of organic template agent, silicon source, aluminum source, potassium hydroxide, and water was 2.74:27.2:1:21.9:479.51, with the silicon source calculated as SiO2 and the aluminum source as Al2O3.

[0065] The initial reaction gel was transferred into a high-pressure reactor and crystallized at 160°C for 48 hours. Then it was filtered and the resulting solid material was dried at 100°C for 12 hours. After that, the sample was placed in a muffle furnace and calcined at 500°C for 6 hours to obtain SSZ-16 zeolite molecular sieve with template agent removed, which was denoted as C-SSZ-16-DABCO sample.

[0066] The C-SSZ-16-DABCO sample was stirred and mixed at room temperature for 3 hours according to the ratio of mass of the sample to volume of ammonium chloride solution (0.1 mol / L) S / L = 1 g: 50 mL. The mixture was then filtered, and the resulting solid material was washed with deionized water and dried at 100℃ for 12 hours to obtain ammonium type SSZ-16 zeolite molecular sieve, denoted as NH4-SSZ-16-DABCO sample.

[0067] The NH4-SSZ-16-DABCO sample was mixed with 0.1 mol / L lithium chloride solution at a solid-liquid ratio of 1 g: 50 mL at room temperature for 3 h, then filtered. The resulting solid material was washed with deionized water and dried at 100 °C for 12 h. Finally, it was calcined in a muffle furnace at 500 °C for 4 h to obtain the modified SSZ-16 zeolite molecular sieve, denoted as Li-SSZ-16-DABCO zeolite molecular sieve.

[0068] Example 2

[0069] According to the ratio of mass of NH4-SSZ-16-DABCO sample to volume of sodium chloride solution (S / L = 1g:50mL), the ammonium-type SSZ-16 zeolite molecular sieve prepared in Example 1 and 0.1mol / L sodium chloride solution were stirred and mixed at room temperature for 3h, then filtered. The resulting solid material was washed with deionized water, dried at 100℃ for 12h, and then calcined in a muffle furnace at 500℃ for 4h to obtain the modified SSZ-16 zeolite molecular sieve, denoted as Na-SSZ-16-DABCO zeolite molecular sieve.

[0070] Example 3

[0071] According to the ratio of mass of NH4-SSZ-16-DABCO sample to volume of potassium chloride solution (S / L = 1g:50mL), the ammonium-type SSZ-16 zeolite molecular sieve prepared in Example 1 and 0.1mol / L potassium chloride solution were stirred and mixed at room temperature for 3h, then filtered. The resulting solid material was washed with deionized water, dried at 100℃ for 12h, and then calcined in a muffle furnace at 500℃ for 4h to obtain the modified SSZ-16 zeolite molecular sieve, denoted as K-SSZ-16-DABCO type zeolite molecular sieve.

[0072] Example 4

[0073] Preparation of the organic template agent Et6-diquat-4dibromide:

[0074] Triethylamine was mixed with 1,4-dibromobutane and methanol in a molar ratio of 2:1:3 and stirred at room temperature for 24 hours. After the reaction was completed, the solid product was washed with diethyl ether and dried in an oven at 50°C for 12 hours to obtain the organic template agent Et6-diquat-4dibromide (1,4-butane-ethane dibromide, abbreviated as Et6-diquat-4).

[0075] Preparation of modified SSZ-16 zeolite molecular sieve:

[0076] Under stirring conditions at room temperature, 5.722 g of organic template agent Et6-diquat-4 was added to 43.15 mL of water and stirred until homogeneous. 8.759 g of MFI zeolite (Si / Al ratio Si = 13.6) was added as both silicon and aluminum sources and stirred for 1 day. Then, 6.142 g of potassium hydroxide was slowly added and stirred to dissolve, resulting in a homogeneous initial reaction gel. The molar ratio of organic template agent, silicon source, aluminum source, potassium hydroxide, and water was 2.74:27.2:1:21.9:479.51, with the silicon source calculated as SiO2 and the aluminum source as Al2O3.

[0077] The initial reaction gel was transferred to a high-pressure reactor and crystallized at 160°C for 48 hours. After filtration, the resulting solid material was dried at 100°C for 12 hours. The solid sample was then calcined in a muffle furnace at 500°C for 6 hours. The solid sample was stirred and mixed at room temperature for 3 hours according to the ratio of mass of calcined solid sample to volume of ammonium chloride solution (0.1 mol / L) S / L = 1 g: 50 mL. After filtration, the solid material was washed with deionized water and dried at 100°C for 12 hours to obtain ammonium type SSZ-16 zeolite molecular sieve, denoted as NH4-SSZ-16-Et zeolite molecular sieve.

[0078] NH4-SSZ-16-Et zeolite molecular sieve was mixed with 0.1 mol / L sodium chloride solution at a solid-liquid ratio of 1 g: 50 mL at room temperature for 3 h, then filtered. The resulting solid material was washed with deionized water and dried at 100 °C for 12 h. Finally, it was calcined in a muffle furnace at 500 °C for 4 h to obtain modified SSZ-16 zeolite molecular sieve, denoted as Na-SSZ-16-Et zeolite molecular sieve.

[0079] Comparative Example 1

[0080] According to the ratio of mass of NH4-SSZ-16-DABCO sample to volume of cesium chloride solution S / L = 1g:50mL, the ammonium type SSZ-16 zeolite molecular sieve prepared in Example 1 and 0.1mol / L cesium chloride solution were stirred and mixed at room temperature for 3h, then filtered. The resulting solid material was washed with deionized water, dried at 100℃ for 12h, and then calcined in a muffle furnace at 500℃ for 4h to obtain the modified SSZ-16 zeolite molecular sieve, denoted as Cs-SSZ-16-DABCO type zeolite molecular sieve.

[0081] Comparative Example 2

[0082] The NH4-SSZ-16-DABCO zeolite molecular sieve sample was calcined in a muffle furnace at 500℃ for 4 hours to obtain unmodified SSZ-16 zeolite molecular sieve, denoted as H-SSZ-16-DABCO zeolite molecular sieve.

[0083] Figure 1 The images show the XRD patterns of the modified SSZ-16 zeolite molecular sieves prepared in Examples 1-4 and the zeolite molecular sieves obtained in Comparative Examples 1-2. Figure 1 It can be seen that all samples are pure-phase SSZ-16 zeolite molecular sieves, and there are no other impurities.

[0084] Figure 2 SEM images of the modified SSZ-16 zeolite molecular sieves prepared in Examples 1-4 and the zeolite molecular sieves obtained in Comparative Examples 1-2 are shown. Figure 2 It can be seen that all the prepared samples mainly exist in the form of spindle morphology.

[0085] Table 1 shows the ICP test results of the modified SSZ-16 zeolite molecular sieves prepared in Examples 1-4 and the zeolite molecular sieves obtained in Comparative Examples 1-2:

[0086] Table 1. ICP test results of zeolite molecular sieves in the examples and comparative examples.

[0087]

[0088] In Table 1, the degree of exchange refers to the ratio of the molar amount of alkali metal cations to the molar amount of aluminum in the zeolite. As shown in Table 1, the degree of exchange for Li-SSZ-16-DABCO is 29.88%; for Na-SSZ-16-DABCO, it is 79.55%; for K-SSZ-16-DABCO, it is 86.54%; for Cs-SSZ-16-DABCO, it is 14.03%; and for Na-SSZ-16-Et, it is 79.05%.

[0089] Application examples

[0090] The modified SSZ-13 zeolite molecular sieves prepared in Examples 1-4, the Cs-SSZ-16-DABCO type zeolite molecular sieve prepared in Comparative Example 1, and the unmodified H-SSZ-16-DABCO zeolite molecular sieve prepared in Comparative Example 2 were subjected to gas selective adsorption and separation tests. Before the test, all zeolite molecular sieve samples were activated at 250°C under vacuum for 6 hours. After the samples cooled to room temperature, single-component gas isothermal adsorption-desorption tests were performed at a test temperature of 298K and a test pressure of 0-1 bar.

[0091] Figure 3 The CO2 adsorption isotherms at 298 K are for the modified SSZ-16 zeolite molecular sieves prepared in Examples 1-4, the Cs-SSZ-16-DABCO of Comparative Example 1, and the unmodified H-SSZ-16-DABCO zeolite molecular sieve of Comparative Example 2. Figure 4 CH4 adsorption isotherms at 298 K for the modified SSZ-16 zeolite molecular sieves prepared in Examples 1-4, Cs-SSZ-16-DABCO of Comparative Example 1, and the unmodified H-SSZ-16 zeolite molecular sieve of Comparative Example 2. Figure 5The N2 adsorption isotherms at 298 K are shown for the modified SSZ-16 zeolite molecular sieves prepared in Examples 1-4, Cs-SSZ-16 of Comparative Example 1, and the unmodified H-SSZ-16 zeolite molecular sieve of Comparative Example 2. Table 2 lists the carbon dioxide separation performance data for the modified SSZ-16 zeolite molecular sieves prepared in Examples 1-4, Cs-SSZ-16-DABCO of Comparative Example 1, and the unmodified H-SSZ-16-DABCO zeolite molecular sieve of Comparative Example 2.

[0092] Table 2 shows the carbon dioxide separation performance data for zeolite molecular sieves in Examples 1-4 and Comparative Examples 1-2.

[0093]

[0094] As can be seen from Table 2, the modified M-SSZ-16-DABCO (M=Li) prepared in this invention... + Na + K + Compared to Cs-SSZ-16-DABCO and unmodified H-SSZ-16-DABCO zeolite molecular sieves, the zeolite molecular sieve exhibits superior CO2 / N2 and CO2 / CH4 gas adsorption and separation performance, demonstrating excellent selective CO2 adsorption. Meanwhile, the CO2 adsorption and separation performance of the Na-SSZ-16-Et sample with Et6-diquat-4 template is essentially comparable to that of the Na-SSZ-16-DABCO sample with DABCO2-diquat-4 template.

[0095] 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 SSZ-16 zeolite molecular sieve, characterized in that, Includes the following steps: The silicon source, aluminum source, alkali source, template agent and water are mixed to obtain the initial reaction gel; The initial reactive gel was crystallized to obtain SSZ-16 zeolite molecular sieve. After the SSZ-16 zeolite molecular sieve is first calcined, it is mixed with ammonium chloride solution for first ion exchange to obtain ammonium-type SSZ-16 zeolite molecular sieve. The ammonium-type SSZ-16 zeolite molecular sieve was mixed with a metal cation solution for a second ion exchange, followed by a second calcination to obtain the modified SSZ-16 zeolite molecular sieve; the cation in the metal cation solution was Li. + Na + and K + One or more of them.

2. The preparation method according to claim 1, characterized in that, The silicon source includes one or more of LTA zeolite, FAU zeolite, MFI zeolite, silica sol, tetraethyl orthosilicate, sodium silicate, and silica. The aluminum source includes one or more of aluminum hydroxide, aluminum oxide, aluminum chloride, aluminum sulfate, sodium aluminate, boehmite, FAU zeolite, LTA zeolite, and MFI zeolite. The alkaline source includes hydroxides; The template agent includes Et6-diquat-n dibromide and / or DABCO2-diquat-mdibromide, where n = 2 to 10, m = 2 to 10, and m and n are both integers.

3. The preparation method according to claim 1 or 2, characterized in that, The silicon source and aluminum source are calculated as SiO2 and Al2O3, respectively, and the molar ratio of the template agent, silicon source, aluminum source, alkali source and water is (0.5~7):(3~80):1:(5~100):(200~1000).

4. The preparation method according to claim 1, characterized in that, The crystallization temperature is 110–220°C, and the time is 1–10 days.

5. The preparation method according to claim 1, characterized in that, The first calcination temperature is 400–600℃ and the time is 5–10 h; the second calcination temperature is 400–800℃ and the time is 3–8 h.

6. The preparation method according to claim 1, characterized in that, The concentration of the ammonium chloride solution is 0.05–10 mol / L, the temperature of the first ion exchange is 20–100 °C, and the time is 2–24 h.

7. The preparation method according to claim 1, characterized in that, The concentration of the metal cation solution is 0.01–10 mol / L, and the temperature of the second ion exchange is 20–100 °C, while the time is 2–24 h.

8. The modified SSZ-16 zeolite molecular sieve prepared by the preparation method according to any one of claims 1 to 7; wherein the modified SSZ-16 zeolite molecular sieve is a metal cation exchange SSZ-16 zeolite molecular sieve, and the metal cation includes Li + Na + and K + One or more of them.

9. The application of the modified SSZ-16 zeolite molecular sieve of claim 8 in the selective adsorption and separation of carbon dioxide in a mixed gas.

10. The application according to claim 9, characterized in that, The mixed gas also includes nitrogen and / or methane.

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