A method for preparing an organic-inorganic hybrid MFI type zeolite molecular sieve membrane

Abstract

The application belongs to the field of gas separation and relates to a preparation method of an organic-inorganic hybrid MFI type zeolite molecular sieve membrane. First, an organic template agent and an organic filler are encapsulated into the pore channel of the zeolite molecular sieve membrane; then the zeolite molecular sieve membrane encapsulating the template agent and the organic filler is irradiated with ultraviolet light to partially decompose the organic molecules in the pore channel, so that the zeolite molecular sieve membrane with an organic-inorganic hybrid structure is formed. The zeolite molecular sieve membrane prepared by the method exhibits excellent gas separation performance and has a broad market application prospect in the field of industrial gas separation and purification and environmental governance.

Description

Technical Field

[0001] This invention relates to the field of gas separation, and in particular to a method for preparing an organic-inorganic hybrid MFI type zeolite molecular sieve membrane. This method can improve the separation selectivity of the zeolite membrane for small molecule gases and can be widely used in gas purification, industrial gas separation and other applications. Background Technology

[0002] Zeolite molecular sieves possess a regular pore structure with pore sizes typically at the molecular level, enabling the separation of molecules of varying sizes. Therefore, zeolite membranes serve as high-performance porous separation materials, widely used in gas separation, pervaporation, and other fields. However, traditional zeolite membrane preparation techniques often rely on the complete decomposition of organic template agents under high-temperature conditions to fully open the pores of the zeolite membrane. This high-temperature treatment method is not only energy-intensive but also leads to partial damage to the zeolite membrane structure, affecting its separation performance.

[0003] Pure silicon MFI zeolite membranes exhibit strong hydrophobicity and relatively large pore sizes (~0.55 nm), making them generally unsuitable for the dehydration and separation of organic compounds and the separation of small molecule gases. Chinese patent document CN119461408A discloses an MFI zeolite membrane with an all-silica framework and hydrophilic pore walls, its preparation method, and its applications. This MFI zeolite membrane encapsulates hydrophilic small molecule organic compounds within the molecular sieve channels, allowing for control over the pore size of the zeolite molecular sieve membrane and effectively increasing the hydrophilicity of the permeation channels within the MFI membrane. Compared to conventional MFI zeolite molecular sieve membranes, this zeolite membrane combines superior acid resistance with a smaller average pore size and good hydrophilicity, making it suitable for the efficient dehydration and separation of organic compounds, particularly for the separation of water / organic mixtures in strongly acidic environments. However, the MFI zeolite membrane prepared by the above method does not perform ideally for separating small molecule gas mixtures. Summary of the Invention

[0004] To address the aforementioned problems, this invention provides a method for preparing an organic-inorganic hybrid MFI type zeolite molecular sieve membrane.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A method for preparing an organic-inorganic hybrid MFI type zeolite molecular sieve membrane includes the following steps:

[0007] (1) The organic template agent and the organic filler are encapsulated together into the pores of the zeolite molecular sieve membrane;

[0008] (2) The zeolite molecular sieve membrane encapsulated with template agent and organic filler is irradiated with ultraviolet light to partially decompose the organic molecules in the pores and form an organic-inorganic hybrid structure zeolite molecular sieve membrane.

[0009] Preferably, the specific method of step (1) is as follows: the carrier is placed in a synthesis liquid containing a template agent and an organic filler, and the template agent and the organic filler are encapsulated together into the pores of the synthesized zeolite molecular sieve membrane by hydrothermal crystallization.

[0010] Preferably, the organic filler in step (1) is dimethylamine, trimethylamine, pentylamine, hexylamine, heptylamine, cyclohexylamine, N,N-dimethylethanolamine, N-methylpentylamine, N-ethylformamide, or dimethylethylenediamine. More preferably, the organic filler is trimethylamine, cyclohexylamine, or N,N-dimethylethanolamine.

[0011] Preferably, the template agent in step (1) is tetrapropylammonium chloride (TPACl).

[0012] More preferably, the synthesis solution in step (1) is a mixture of tetraethyl orthosilicate, template agent, filler, sodium hydroxide, and water, with a molar ratio of 1:0.05-2:0.01-4:0.05-0.4:20-150. More preferably, the molar ratio of tetraethyl orthosilicate, template agent, filler, sodium hydroxide, and water is 1:0.1-1:0.1-2:0:1-0.3:40-100. Even more preferably, it is 1:0.25-0.3:0.1-0.3:0.15-0.2:60-100.

[0013] Preferably, the hydrothermal crystallization conditions in step (1) are: 120-200℃, 10-60h. More preferably, they are 140-180℃, 12-48h.

[0014] Preferably, the ultraviolet light wavelength mentioned in step (2) is 100-400nm. More preferably, it is 185-254nm.

[0015] Preferably, the ultraviolet light irradiation intensity in step (2) is 0.01-100 mW / cm². More preferably, it is 0.1-40 mW / cm². More preferably, it is 1-10 mW / cm².

[0016] Preferably, the ultraviolet irradiation time in step (2) is from 1 to 300 hours. More preferably, it is 40 to 120 hours.

[0017] Preferably, the ultraviolet irradiation temperature in step (2) is 0-100℃. More preferably, it is 20-70℃. More preferably, it is 25-40℃.

[0018] Preferably, the average pore size of the organic-inorganic hybrid zeolite molecular sieve membrane obtained after the decomposition of organic molecules in step (2) is 0.3~0.5 nm.

[0019] This invention also provides the application of the organic-inorganic hybrid zeolite molecular sieve membrane prepared by the above method in gas separation. The gases are He, H2, CO2, N2, CH4, C2H6, C3H8, and SF6. Preferably, it is more suitable for separating CO2 / CH4, N2 / SF6, and H2 / CH4. The selectivity can reach 82, 114, and 55, respectively. The CO2 permeability is 2 × 10⁻⁶. -7 mol·Pa -1 ·s -1 ·m -2 N2 penetration rate can reach 6.5×10 -8 mol·Pa -1 ·s -1 ·m -2 H2 permeability is 3.1 × 10⁻⁶ -7 mol·Pa -1 ·s -1 ·m -2 .

[0020] The beneficial effects of this invention are:

[0021] For water / organic matter separation systems, the control of the surface chemical properties of zeolite membranes is particularly important; however, for the separation of small molecule gases, the precision required for controlling the average pore size and pore size distribution of the membrane is far greater than that required for water / organic matter separation systems. To achieve efficient separation of small molecule gas mixtures using mesoporous MFI zeolite membranes, it is necessary to further screen the types of organic molecules encapsulated in the pores of the MFI zeolite membrane and to more precisely control their decomposition behavior, thereby achieving precise control over the pore structure of the zeolite membrane.

[0022] The method of this invention, by selecting ideal template agents and organic fillers and encapsulating them in situ into the pores of an MFI zeolite membrane before radiation decomposition, enables precise control of the pore size of the zeolite membrane at the sub-nanometer level. This results in the effective pore radial micropore size of the mesoporous MFI zeolite membrane being close to that of the micropores. The uniform micropore structure and narrow pore size distribution give it extremely high selectivity for the separation of small molecule gases, significantly expanding the application fields of MFI zeolite membranes. Attached Figure Description

[0023] Figure 1 The XRD patterns are those of the support, seed layer support, and synthesized MFI zeolite membrane in Example 1.

[0024] Figure 2The images show SEM images of the carrier (a, d), the seed-coated carrier (b, e), and the MFI zeolite membrane (c, f) in Example 1. Detailed Implementation

[0025] The raw materials used in the embodiments and comparative examples of this invention are all commercially available products.

[0026] Example 1

[0027] Preparation of organic-inorganic hybrid MFI zeolite molecular sieve membranes:

[0028] (1) Loading seed crystals onto an alumina support:

[0029] Tetrapropylammonium hydroxide (TPAOH) was mixed evenly with deionized water, and then added dropwise to a tetraethyl silicate (TEOS) solution. The mixture was stirred at 600 rpm for 6 h to obtain a synthesis solution with a molar ratio of 1.0 TEOS: 5 TPAOH: 10 H2O.

[0030] The synthesis solution was transferred to a reaction vessel and subjected to hydrothermal crystallization at 150°C for 48 h. The obtained product was repeatedly washed with deionized water until neutral, and then ultrasonically dispersed in deionized water to prepare a seed solution of 1.5 mg / mL. The seed crystals were loaded onto an alumina support (average pore size 200 nm) by impregnation, and then calcined in a muffle furnace at 500°C for 8 h to obtain a support pre-coated with a seed layer.

[0031] (2) Encapsulating organic template agents and organic fillers:

[0032] A synthesis solution with a molar ratio of 1.0 TEOS: 0.3 TPACl: 0.1 S: 0.2 NaOH: 60 H2O (where S is the filler trimethylamine) was prepared and placed in a reaction vessel with a support pre-coated with seed crystals. Hydrothermal crystallization was carried out at 180℃ for 24 hours. After the reaction, the zeolite membrane was removed and rinsed with deionized water until neutral. Finally, the moisture was dried to obtain the synthesized MFI zeolite membrane.

[0033] (3) Ultraviolet radiation treatment:

[0034] The MFI zeolite membrane was irradiated with a 254nm UV lamp for 48 hours (10 mw / m). 2 (25℃) to partially decompose the organic matter in the pores of the zeolite membrane, and finally obtain an organic-inorganic hybrid MFI zeolite molecular sieve membrane.

[0035] Figure 1The XRD patterns of the alumina support, the seed-coated support, and the synthesized MFI zeolite membrane used in Example 1 show that the characteristic diffraction peaks of the synthesized MFI membrane are completely consistent with the standard card (PDF#44-0696) of MFI zeolite, and no other impurity peaks were observed. It can be confirmed that this example successfully prepared high-purity MFI zeolite molecular sieve. Figure 2 (a) is a SEM image of the carrier surface. Figure 2 (d) is a SEM image of the carrier cross section, which shows that the carrier surface has large pores. Figure 2 (b, e) are SEM images of the surface and cross-section of the carrier coated with the seed layer. It can be seen that after coating with the seed layer, the original porous structure of the carrier is filled, and the carrier surface becomes smooth. The seed particle size is approximately 200 nm, and the seed layer thickness is approximately 2 μm. Figure 2 (c,f) are SEM images of the synthesized MFI zeolite film. It can be seen that the grains of the MFI film grow in an alternating manner. The thickness of the MFI zeolite film is about 8 μm, and the surface is dense with no obvious defects.

[0036] To evaluate the permeability and selectivity of the zeolite membrane, the prepared organic-inorganic hybrid MFI zeolite molecular sieve membrane was placed in a stainless steel membrane module and sealed with O-rings. The single-gas permeability of the membrane was measured at room temperature, with an inlet-side pressure of 0.2 MPa and a permeate-side pressure of 0.1 MPa. The CO2 permeability of the organic-inorganic hybrid MFI zeolite molecular sieve membrane was found to be 2 × 10⁻⁶. - 7 mol·Pa -1 ·s -1 ·m -2 The CO2 / CH4 selectivity is 82%.

[0037] Example 2

[0038] Preparation of organic-inorganic hybrid MFI zeolite molecular sieve membranes:

[0039] (1) The preparation of the seed layer on the alumina carrier is the same as in Example 1.

[0040] (2) Prepare a synthesis solution with a molar ratio of 1.0 TEOS:0.25 TPACl:0.3 S:0.15 NaOH:70H2O (where S is the filler cyclohexylamine), and place it in a reaction vessel with a support pre-coated with seed crystals. Perform hydrothermal crystallization at 160℃ for 36 h. After the reaction is complete, remove the zeolite membrane and rinse it with deionized water until neutral. Finally, dry the water to obtain the synthesized MFI zeolite membrane.

[0041] (3) The MFI zeolite membrane was placed under a UV lamp with a wavelength of 185 nm and irradiated for 120 h (4 mw / m 2(40℃) to partially decompose the organic matter in the pores of the zeolite membrane, and finally obtain an organic-inorganic hybrid MFI zeolite molecular sieve membrane.

[0042] The method for evaluating the permeability and selectivity of the organic-inorganic hybrid MFI zeolite molecular sieve membrane was the same as in Example 1, and the N2 permeability of the organic-inorganic hybrid MFI zeolite molecular sieve membrane was found to be 6.5 × 10⁻⁶. -8 mol·Pa -1 ·s -1 ·m -2 The N2 / SF6 selectivity is 114.

[0043] Example 3

[0044] (1) The preparation of the seed layer on the alumina carrier is the same as in Example 1.

[0045] (2) Prepare a synthesis solution with a molar ratio of 1.0 TEOS: 0.3 TPACl: 0.2 S: 0.2 NaOH: 100H2O (where S is the filler N,N-dimethylethanolamine), and place it in a reaction vessel with a support pre-coated with seed crystals. Perform hydrothermal crystallization at 160℃ for 36 h. After the reaction is complete, remove the zeolite membrane and rinse it with deionized water until neutral. Finally, dry the water to obtain the synthesized MFI zeolite membrane.

[0046] (3) The MFI zeolite membrane was placed under a 0.3cm ultraviolet lamp with a wavelength of 254nm and irradiated for 72 h (1mw / m 2 (30℃) to partially decompose the organic matter in the pores of the zeolite membrane, and finally obtain an organic-inorganic hybrid MFI zeolite molecular sieve membrane.

[0047] The method for evaluating the permeability and selectivity of the organic-inorganic hybrid MFI zeolite molecular sieve membrane was the same as in Example 1, and the H2 permeability of the organic-inorganic hybrid MFI zeolite molecular sieve membrane was found to be 3.1 × 10⁻⁶. -7 mol·Pa -1 ·s -1 ·m -2 The H2 / CH4 selectivity is 55.

[0048] Comparative Example 1

[0049] Compared with Example 1, the difference is that step (3) uses high-temperature calcination to decompose the organic matter in the pores of the MFI zeolite membrane.

[0050] The MFI zeolite membrane was placed in a muffle furnace and calcined at 500℃ for 8 hours in air at a rate of 0.5℃ / min, followed by a cooling to room temperature at a rate of 0.5℃ / min. The resulting organic-inorganic hybrid MFI zeolite molecular sieve membrane had a CO2 permeability of 8.4 × 10⁻⁶. -7 mol·Pa -1 ·s -1 ·m -2 However, its CO2 / CH4 selectivity is only 5.5, indicating that the average pore size of the zeolite molecular sieve membrane is relatively large.

[0051] Comparative Example 2

[0052] Compared to Example 2, the difference lies in the preparation conditions of the MFI zeolite membrane: except for the use of high-temperature calcination to decompose the organic matter in the pores of the MFI zeolite membrane, the other preparation conditions are the same as in Example 2. The calcination process is as follows: the MFI zeolite membrane is placed in a muffle furnace and calcined at 500°C for 8 h in an air atmosphere at a rate of 0.5°C / min, followed by a cooling to room temperature at a rate of 0.5°C / min. The resulting MFI membrane has an N2 permeability of 2.6 × 10⁻⁶. -7 mol· Pa -1 ·s -1 ·m -2 However, its N2 / SF6 selectivity is only 3.2, indicating that the average pore size of the zeolite molecular sieve membrane is relatively large.

[0053] Comparative Example 3

[0054] The difference from Example 3 is as follows:

[0055] N,N-dimethylethanolamine was not added to the synthesis solution in step (2). The resulting organic-inorganic hybrid MFI zeolite molecular sieve membrane had an H2 permeability of 3.3 × 10⁻⁶. -7 mol·Pa⁻¹·s -1 ·m -2 However, its H2 / CH4 selectivity is only 7.5, indicating that the average pore size of the zeolite molecular sieve membrane is relatively large.

[0056] Comparative Example 4

[0057] Compared to Example 2, the difference lies in the absence of cyclohexylamine in the synthesis solution of step (2). The resulting organic-inorganic hybrid MFI zeolite molecular sieve membrane has an N2 permeability of 4.2 × 10⁻⁶. -8 mol·Pa -1 ·s -1 ·m -2 However, its N2 / SF6 selectivity is only 25, indicating that the average pore size of the zeolite molecular sieve membrane is relatively large.

[0058] Comparative Example 5

[0059] The difference from Example 3 is that, in accordance with Chinese Patent Document CN119461408A, an ozone atmosphere is used to decompose the organic matter in the pores of the MFI zeolite membrane.

[0060] The process of ozone decomposition of organic matter in the pores of an MFI zeolite membrane is as follows: The MFI zeolite membrane is placed in a tubular furnace and heated to 150°C at a rate of 0.5°C / min. Then, an ozone / oxygen mixture is introduced into the furnace and maintained for 20 hours, followed by cooling to room temperature at a rate of 0.5°C / min. The resulting MFI zeolite membrane has an H2 permeability of 4.6 × 10⁻⁶. -7 mol·Pa -1 ·s -1 ·m -2 The H2 / CH4 selectivity was only 4.3, indicating that the average pore size of the zeolite molecular sieve membrane was relatively large.

Claims

1. A method for preparing an organic-inorganic hybrid MFI type zeolite molecular sieve membrane, characterized by, The method comprises the following steps: (1) encapsulating the organic template agent and the organic filler into the pores of the zeolite molecular sieve membrane: placing a carrier into a synthesis solution containing the organic template agent and the organic filler, and encapsulating the organic template agent and the organic filler into the pores of the synthesized zeolite molecular sieve membrane through hydrothermal crystallization; the organic filler is one or a combination of dimethylamine, trimethylamine, pentylamine, hexylamine, heptylamine, cyclohexylamine, N,N-dimethylethanolamine, N-methylpentylamine, N-ethylformamide, and dimethyl ethylenediamine, and the organic template agent is tetrapropylammonium chloride; the synthesis solution is prepared by mixing tetraethyl orthosilicate, the organic template agent, the organic filler, sodium hydroxide, and water, and the molar ratio of tetraethyl orthosilicate, the organic template agent, the organic filler, sodium hydroxide, and water is 1:0.05-2:0.01-4:0.05-0.4:20-150; the hydrothermal crystallization conditions are 120-200 ℃ and 10-60 h; (2) irradiating the zeolite molecular sieve membrane encapsulating the organic template agent and the organic filler with ultraviolet light to partially decompose the organic molecules in the pores and form a zeolite molecular sieve membrane with an organic-inorganic hybrid structure; the wavelength of the ultraviolet light is 100-400 nm; the ultraviolet light irradiation intensity is 0.01-100 mW / cm²; the ultraviolet light irradiation time is 1-300 hours; and the ultraviolet light irradiation temperature is 0-100 ℃.

2. The production method according to claim 1, characterized by, the organic filler is one or a combination of trimethylamine, cyclohexylamine, and N,N-dimethylethanolamine.

3. The preparation method according to claim 1, characterized in that, the molar ratio of tetraethyl orthosilicate, the organic template agent, the organic filler, sodium hydroxide, and water is 1:0.1-1:0.1-2:0.1-0.3:40-100.

4. The method of claim 1, wherein, in step (2), the wavelength of the ultraviolet light is 185-254 nm; the ultraviolet light irradiation intensity is 0.1-40 mW / cm²; the ultraviolet light irradiation time is 40-120 h; and the ultraviolet light irradiation temperature is 20-70 ℃.

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