A method for statically synthesizing STT molecular sieve membrane, STT molecular sieve membrane and its application in separating H2

Abstract

The present invention discloses a method for statically synthesizing an STT molecular sieve membrane, an STT molecular sieve membrane and its application in separating H2. The method for statically synthesizing an STT molecular sieve membrane comprises the following steps: coating SiO2 particles on the surface of a support and then calcining; coating small-particle-size STT molecular sieve seed crystals on the surface of the calcined support; placing the coated support in a synthetic liquid and performing hydrothermal synthesis under static conditions; the synthetic liquid after the reaction is semi-solid, and the molar ratio of the raw materials in the synthetic liquid is: 1SiO2: (0.1-0.3) TMAdaOH: (40-130) H2O; after cleaning and drying, roasting in an ozone atmosphere to remove the template. The method adjusts the water content, and the liquid synthetic liquid is converted into a semi-solid gel in situ to avoid the sedimentation of nutrients, and the seed crystals gradually grow and fuse together to form an STT molecular sieve membrane. Since the nucleation process of the semi-solid synthetic liquid precursor is suppressed, the amorphous precursor can be reused for the synthesis of the membrane. The STT molecular sieve membrane exhibits excellent separation performance for high-pressure H2 / CH4 mixtures.

Description

Technical Field

[0001] The present invention relates to a method for statically synthesizing an STT molecular sieve membrane, an STT molecular sieve membrane and an application thereof in separating H2, and belongs to the technical field of molecular sieve membranes. Background Art

[0002] H2 / CH4 separation is not only an important step in coke oven gas purification, but also an equally important process in the separation of hydrogen blending terminals in natural gas pipelines. For pipeline hydrogen transmission, the pipeline operating pressure is generally 1-4MPa.

[0003] Physical aging is a problem for polymer membranes because their pore structures are thermodynamically metastable. Molecular sieve membranes are widely used in CO₂ / CH₄ separation due to their preferential adsorption and rapid reverse osmosis. However, due to their competitive adsorption, their use for H₂ / CH₄ separation has been limited.

[0004] The pore size of STT molecular sieve in the [-101] direction is 0.24×0.35nm (seven-membered ring, 7MR), and the pore size in the

[101] direction is 0.37×0.53nm (nine-membered ring, 9MR). The unique pores ensure that the STT molecular sieve membrane has an excellent size exclusion effect for H2 / CH4 separation. Due to the use of hydrofluoric acid (HF) and long synthesis time, STT molecular sieve membranes have rarely been studied. In the past two years, the synthesis of STT molecular sieve membranes using fluorine-free precursors has been reported. However, since the autoclave must be rotated during the hydrothermal synthesis process, the synthesis process is relatively complicated. In addition, only a small amount of nutrients participate in the mutual growth of the membrane, which increases the manufacturing cost and the amount of chemical waste. Summary of the Invention

[0005] The first purpose of the present invention is to solve the problem of rotational synthesis in the preparation process of high-quality STT molecular sieve membranes, and to provide a method for static synthesis of STT molecular sieve membranes. By adjusting the water content, the liquid precursor is converted into a semi-solid state in situ to avoid nutrient precipitation. The seed crystals gradually grow and fuse together to form an STT molecular sieve membrane.

[0006] The second object of the present invention is to provide a method for preparing small-particle STT molecular sieve, which can well form a continuous and uniform seed layer as a seed crystal.

[0007] The third purpose of the present invention is to provide a method for recycling STT molecular sieve synthesis liquid. Since the nucleation process of the semi-solid synthesis liquid precursor is inhibited, the amorphous precursor can be reused for membrane synthesis, and the STT molecular sieve membrane also exhibits excellent separation performance for high-pressure H2 / CH4 mixtures.

[0008] In order to achieve the above object, the technical solution adopted by the present invention is:

[0009] A method for preparing an STT molecular sieve membrane by static synthesis comprises the following steps:

[0010] S1, coating SiO2 particles on the surface of the support and then calcining;

[0011] S2, coating STT molecular sieve seed crystals on the surface of the calcined support;

[0012] S3, placing the coated support in a synthesis liquid and performing hydrothermal synthesis under static conditions; the synthesis liquid after the reaction is semi-solid, and the molar ratio of the raw materials in the synthesis liquid is: 1SiO2: (0.1-0.3) TMAdaOH: (40-130) H2O;

[0013] S4. After cleaning and drying, the template is removed by calcination in an ozone atmosphere.

[0014] Preferably, in step S1, the support body is made of alumina hollow fibers with multiple channels;

[0015] The average pore size of the alumina hollow fiber is in the range of 50-500 nm, and the porosity is 20-50%;

[0016] The calcination conditions are: 600-1000K, 6-10h.

[0017] Preferably, in step S2, the STT molecular sieve seed crystals are coated with an aqueous suspension containing 0.3-1.2% of small-particle-size STT molecular sieve seed crystals;

[0018] The synthesis method of the small-particle STT molecular sieve seed crystals is as follows: SiO2, NaOH, Al(OH)3, TMAdaOH and H2O are mixed to obtain a mixed solution, and then conventional STT molecular sieve seed crystals are added to the mixed solution, and the mixture is obtained through hydrothermal crystallization;

[0019] Wherein, in the mixed solution, the molar ratio of SiO2, NaOH, Al(OH)3, TMAdaOH and H2O is: 1:(0.1-0.3):(0.002-0.01):(0.1-0.5):(130-180);

[0020] The mass concentration of conventional STT molecular sieve seeds added to the mixed solution is 0.05-0.2wt.%;

[0021] The conditions for hydrothermal crystallization are: 400-550K, 10-48h.

[0022] Preferably, in step S3, the static condition includes no rotation during the hydrothermal synthesis process;

[0023] The conditions for hydrothermal synthesis are: 400-550K, 24-120h.

[0024] Preferably, 0.001-0.15 wt.% of small-particle-size STT molecular sieve seeds are also added to the synthesis liquid.

[0025] Preferably, the molar ratio of raw materials in the synthetic solution is 1SiO2:0.2TMAdaOH:84H2O.

[0026] Preferably, in step S4, the calcination conditions in the ozone atmosphere are: 450-500K, 48-100h.

[0027] A method for recycling synthetic liquid for repeated preparation of STT molecular sieve membrane is to recover synthetic liquid with a raw material molar ratio of 1SiO2:0.2TMAdaOH:84H2O, add 5-20wt.% of TMAdaOH solution to the recovered synthetic liquid, and then prepare the STT molecular sieve membrane.

[0028] An STT molecular sieve membrane is prepared by any of the above methods.

[0029] The above-mentioned STT molecular sieve membrane is used in the separation of H2, which is used to separate H2 from H2 / CH4 mixed gas, with an operating pressure of 0.1-2.8MPa.

[0030] The beneficial effects of the present invention are:

[0031] 1. Using a static synthesis method and adjusting the water content to convert the reaction solution from liquid to semi-solid can avoid nutrient precipitation, allowing the seed layer to effectively grow into a continuous membrane, thereby preparing high-quality STT molecular sieve membranes;

[0032] 2. After coating the surface of the support with SiO2 particles and calcining them, the SiO2 particles can form an intermediate transition layer on the surface of the macroporous support, thereby preventing the synthesized STT seeds from penetrating into the pores of the support and growing, thereby reducing the separation flux.

[0033] 3. Use directly synthesized small-particle STT molecular sieve as seed crystal, avoiding the use of high-energy ball mills and reducing equipment requirements;

[0034] 4. Since the synthetic liquid after the reaction is semi-solid and has a relatively low crystallinity, the synthetic liquid can be reused, reducing the total amount of chemical waste;

[0035] 5. The H2 permeability and H2 / CH4 mixture selectivity of the STT molecular sieve membrane synthesized under static conditions at normal pressure are 6.1×10 -8 mol·m-2 ·s -1 ·Pa -1 and 115, which are twice as high as those of the membrane synthesized under rotating conditions; and when the feed pressure is 2.1 MPa, the H2 / CH4 selectivity drops to 14, and the H2 flux is 2.0 Nm 3 ·m -2 ·h -1 , which paves the way for the practical application of STT zeolite membranes in H2 separation under high pressure. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 Characterization of small-particle STT molecular sieves. (a) PXRD pattern, (b) N2 adsorption isotherm at 77 K, (c) particle size distribution, and (d) SEM image.

[0037] Figure 2 Schematic diagram of the synthesis of STT zeolite membrane under static conditions.

[0038] Figure 3 SEM images of the upper surface of the hollow fiber. (a) Before crystal coating (b) After crystal coating.

[0039] Figure 4 PXRD characterization of STT molecular sieves prepared with different water contents. (a) In situ synthesis, (b) Secondary growth (addition of 0.001 wt.% seed crystals). Molar composition: 1SiO2:0.2TMAdaOH:yH2O.

[0040] Figure 5 is the relative crystallinity of STT molecular sieves prepared at different water contents (y).

[0041] Figure 6 is the effect of water content (y) on the state of the synthesis liquid precursor before and after hydrothermal synthesis.

[0042] Figure 7 The effect of crystallization time (t) on the state of the synthetic liquid precursor under static conditions. The molar composition is 1SiO2:0.2TMAdaOH:84H2O.

[0043] Figure 8 Figure 5 Characterization of the synthesis liquid precursor after membrane synthesis. (a) SEM image, (b) PXRD pattern.

[0044] Figure 9 Surface (left) and cross-section (right) SEM images of STT molecular sieve membranes synthesized with different water contents (y): (ab) y = 44; (cd) y = 64; (ef) y = 84; (gh) y = 104; (ij) y = 124.

[0045] Figure 10 SEM photos of the surface (left) and cross-section (right) of the STT molecular sieve membrane under rotating conditions.

[0046] Figure 11 PXRD patterns of STT zeolite membranes synthesized at different water contents (y). (a) PXRD, (b) peak area ratios of STT zeolite (2θ = 8.1°, 8.5°, 9.4°, and 10.7°) and α-Al2O3 (2θ = 25.6°), (c) peak area ratios of the 7MR channel (2θ = 8.5° and 9.4°) and the 9MR channel (2θ = 10.7°).

[0047] Figure 12 Characterization of the synthesis liquid precursor after membrane synthesis (10 wt.% TMAdaOH solution was added to the reused precursor). (a) Photograph, (b) PXRD, and (c) SEM.

[0048] Figure 13 The separation performance of equimolar H2 / CH4 mixture of STT zeolite membrane synthesized by reusing synthetic liquid precursor.

[0049] Figure 14 PXRD patterns and SEM images of STT molecular sieve membranes synthesized by reusing the synthetic liquid precursor. (a) PXRD, (b) surface, (c) cross section.

[0050] Figure 15 (a) Gas separation performance of STT zeolite membranes and high-pressure adsorption isotherms of STT zeolites. (b) Ideal and Knudsen selectivities for H2 over other gas molecules. (c) and (d) Isotherms for H2 and CH4 (closed symbols: adsorption points; open symbols: desorption points; lines: Langmuir model fit). (e) Pressure-dependent equimolar H2 / CH4 separation performance.

[0051] Figure 16 SF6 single component permeability of STT zeolite membrane at different pressures at 298K. DETAILED DESCRIPTION

[0052] Example 1 Synthesis of small particle size STT molecular sieve

[0053] The particle size of STT molecular sieve seeds synthesized in hydroxide or fluoride media is usually greater than 5 μm. Although high-energy ball milling technology can effectively reduce the particle size of STT molecular sieve ( Figure 1Area c in the middle). However, ball milling has high requirements on equipment, and STT molecular sieve is easily contaminated by the ball milling material during the ball milling process. The molar composition of the small-particle STT molecular sieve is 1SiO2:0.2NaOH:0.005Al(OH)3:0.2TMAdaOH:164H2O, and 0.1wt.% of conventional STT molecular sieve is added as a seed crystal. Hydrothermal crystallization is carried out in a Teflon-lined autoclave at 453K for 2 days. The average particle size of the synthesized STT molecular sieve is 240nm ( Figure 2 The crystals in region c can be directly used as seeds for subsequent membrane synthesis. The relative crystallinity of STT molecular sieve is defined as 100%.

[0054] In this embodiment, the small-size STT molecular sieve seed crystals were directly synthesized in a synthetic precursor diluted with a certain amount of sodium hydroxide and aluminum hydroxide. Figure 1 The pure phase STT molecular sieve was successfully synthesized (area a in the middle). At 77K, the adsorption of N2 showed a typical type I isotherm with no hysteresis loop ( Figure 1 The BET area and micropore volume are 620 m 2 g -1 and 0.21cm 3 g -1 , which is similar to the STT molecular sieve with a particle size of about 1μm. It has been measured that its surface area is 62m 2 g -1 , slightly larger than the STT molecular sieve (57m 2 g -1 By diluting the synthetic precursor, the crystal size was reduced to 240 nm, which is similar to the size of ball-milled STT molecular sieve (260 nm) ( Figure 1 mid-cd area).

[0055] Example 2 Static Synthesis of STT Molecular Sieve Membrane

[0056] The STT molecular sieve membrane with unique channels is an ideal choice for separating hydrogen (H2) and methane (CH4). However, it can only be successfully synthesized under rotating conditions, which is complicated for scale-up synthesis. Therefore, the present invention provides a static synthesis method to prepare high-quality STT molecular sieve membranes ( Figure 2 The in situ transformation of the precursor from a liquid to a semi-solid state effectively inhibits nucleation in the gel, which does not affect the growth of the seed layer into a continuous film.

[0057] Under static conditions, STT molecular sieve membranes were synthesized on α-Al2O3 four-channel hollow fibers using a precursor with a molar composition of 1SiO2:0.2TMAdaOH:y H2O (y=44-124) as raw material. The average pore size and porosity of the α-Al2O3 four-channel hollow fibers were ~460nm and ~40%, respectively. Before hydrothermal synthesis, SiO2 particles with a particle size of 50nm were coated on the support and calcined at 823K for 8h. Then, the support was impregnated with small-particle STT molecular sieve seeds (0.5wt.%, containing water). The synthesis temperature and synthesis time were fixed at 453K and 4 days. After cleaning and drying after synthesis, the template was removed by calcination in an ozone atmosphere (450K, 2 days). Before hydrothermal synthesis, a uniform seed layer ( Figure 3 middle ab region).

[0058] Comparative Experiment 1 Effect of Seed Crystal on Crystallization of Synthetic Liquid with Different Water Content

[0059] The crystallization effect was further tested by adding 0.001wt.% seed crystals into precursors with different water contents, and the phase composition of the synthetic solution was characterized and analyzed using PXRD. Figure 4 When the water content is y=44, the synthetic liquid finally turns into liquid ( Figure 6 The relative crystallinity reaches 58.4% ( Figure 4 However, at y = 64 and y = 84, the observed semi-solid relative crystallinity was 12.6% and 9.9%, respectively ( Figure 4 When the water content increases to y = 104-124, the relative crystallinity is close to 0%, which is basically equivalent to in situ synthesis ( Figure 4 This confirms that the nucleation of molecular sieves in the main gel is effectively suppressed with the increase of water content. However, when the water content is y = 84, the relative crystallinity increases to 24.7% ( Figure 5 ). This result indicates that high seed loading is beneficial to the mutual growth of STT zeolite membranes.

[0060] Comparative Experiment 2 Effect of Water Content on the Synthesis of STT Molecular Sieve Membrane

[0061] After aging for 12 hours at room temperature, when the water content exceeds y=44, the precursor gradually changes from milky white to a transparent solution ( Figure 6 Under static conditions with a water content of y=44, even if a high-quality STT molecular sieve membrane can be synthesized, the silicon source will precipitate at the bottom ( Figure 6After 4 days of hydrothermal reaction at 453K, the transparent solution transformed into a semi-solid state (y = 64-124) and adhered to the substrate ( Figure 6 (areas d, f, h, and j in the middle).

[0062] In order to study the liquid-solid transformation process, the relationship between the state of the precursor at y = 84 and the crystallization time was further tracked ( Figure 7 ). The clear solution turned into a milky liquid after the initial heating for one hour and then transformed into a semi-solid state in situ. This phenomenon is due to the increase in viscosity caused by the aggregation of silica. In order to analyze the phase composition, SEM and PXRD analysis were performed on the semi-solid gel (molar composition of 1SiO2:0.2TMAdaOH:84H2O). In the SEM images, although the relative crystallinity was 3.8% ( Figure 8 However, no obvious crystals were observed in the precursor with a water content of y = 84 ( Figure 8 (area a in the middle).

[0063] The STT molecular sieve membrane was synthesized at 453K for 4 days using precursors with different water contents (y = 44-124). The membrane layer is closely related to the water content ( Figure 9 Under the condition of relatively low water content y=44, the molecular sieve crystals accumulate on the top surface to form a double-layer membrane with a thickness of 13μm ( Figure 9 The first layer tightly attached to the support is dense and continuous (5 μm), while the second layer is loose (8 μm). This phenomenon is due to the fact that the STT crystal nuclei in the main gel can easily attach to the membrane surface and grow further. This is also the reason why high-performance STT molecular sieve membranes require rotational synthesis ( Figure 10 On the other hand, when the water content is y=84-104, the film layer is uniform and continuous with a thickness of 10μm ( Figure 9 When the water content is y=124, the film thickness is further reduced to 8μm ( Figure 9 In addition, the size of STT crystals on the membrane surface decreases with increasing water content ( Figure 9 This is because the nutrient concentration required for crystal growth decreases.

[0064] The crystalline phase composition of the prepared film was determined by PXRD patterns ( Figure 11 The crystallinity of the molecular sieve was evaluated by calculating the ratio of the above four peak areas to the α-Al2O3 peak area (2θ = 25.6°). Figure 11The ratio decreases with increasing water content, which is consistent with the thinner film layer shown in the SEM image. The orientation of the molecular sieve crystals was quantified by calculating the peak area ratio of 7MR / 9MR ( Figure 11 (c region in the middle). When preparing a membrane with a water content of y = 64, the value is relatively low (240%), which is due to the accumulation of crystals on the membrane surface. However, when the water content is y = 84, the ratio increases rapidly to 620%. In contrast, the ratio of the membrane prepared with the original precursor (y = 44) is only 160%. These results indicate that the diluted precursor makes the 7MR orientation in the STT molecular sieve membrane more ideal.

[0065] The separation performance of the membranes was evaluated using an equimolar H2 / CH4 mixture at 298 K and 0.2 MPa. Three membranes were synthesized under each condition for the separation of H2 / CH4 mixtures (results are shown in Table 1).

[0066] Table 1 Different water content y a Separation performance of the membrane synthesized under static conditions for equimolar H2 / CH4 mixture

[0067]

[0068]

[0069] a:1SiO2:0.2TMAdaOH:y H2O.

[0070] b: At 298K and 0.2MPa, using 200mL·min -1 Equimolar mixture test gas permeability. 50mL·min -1 Argon as purge gas, ×10 -10 mol·m -2 ·s -1 ·Pa -1 .

[0071] c: Rotation synthesis.

[0072] At a water content of y = 44, the average selectivity of H2 / CH4 is 9.4 ± 5.7, indicating the presence of non-molecular sieve pores. Although STT molecular sieve membranes can be prepared with an ideal H2 / CH4 selectivity of 87 at low water content (y = 10.4), HF is inevitably used as a mineralizer. Its performance is also lower than that of membranes synthesized under rotating conditions using ball-milled STT molecular sieve as seeds (α H2 / CH4=62-91). After utilizing rotation in the synthesis, the average H2 / CH4 selectivity was 47±13. Both results indicate that nutrient deposits are the key factor in the poor intergrowth of STT zeolite membranes. At a water content of y=84 (M7-M9), the mixture selectivity increased to 63±15, with an average H2 permeability of 5.8×10 -8 mol·m -2 ·s -1 ·Pa -1 The high selectivity is due to the high proportion of 7MR transport paths on the top surface of the membrane. However, when the water content is further increased to y = 124 (M13-M15), the selectivity drops to 32, and the H2 permeance also drops to 3.4×10 -8 mol·m -2 ·s -1 ·Pa -1 This is due to insufficient mutual growth and channel blockage of amorphous materials in the diluted precursor.

[0073] Example 3: Reusing the Synthetic Liquid Precursor to Synthesize STT Molecular Sieve Membrane

[0074] After the recovered synthetic liquid is reused, the state of the synthetic liquid changes from semi-solid to liquid, and the high crystallinity STT molecular sieve ( Figure 12 The original molar composition of the recovered synthetic solution is 1SiO2:0.2TMAdaOH:84H2O. TMAdaOH aqueous solution is added to the recovered precursor ( Figure 13-14 ) Another STT molecular sieve membrane was synthesized. The separation performance for an equimolar H2 / CH4 mixture is shown in Table 2.

[0075] Table 2 Equimolar H2 / CH4 separation performance of STT molecular sieve membrane prepared by recycling synthetic liquid

[0076]

[0077]

[0078] a: The original molar composition of the precursor is 1SiO2:0.2TMAdaOH:84H2O, and TMAdaOH aqueous solution is directly added to the used precursor.

[0079] b: At 298K and 0.2MPa, using 200mL·min -1 Equimolar mixture test gas permeability. 50mL·min -1 Argon is used as sweep gas, atmospheric pressure is 10 -10 mol·m -2 ·s -1 ·Pa -1 .

[0080] Example 4: Statically prepared STT molecular sieve membrane used for gas separation testing

[0081] Single component permeability test

[0082] The permeation of a single gas was studied using gas molecules with different kinetic diameters ( Figure 15 The STT molecular membrane (M9) shows the largest CO2 permeability, followed by H2>He>N2>CH4>C2H6>SF6, which is similar to the DD3R and SSZ-13 molecular sieve membranes with 8MRs. The ideal selectivity of H2 / N2 is 28, H2 / CH4 is 140, H2 / C2H6 is 310, and H2 / SF6 is 1930, all of which are much higher than the Knudsen selectivity ( Figure 15 The ideal selectivity of H2 / SF6 is even higher than that of the rotational synthesis method, indicating the high quality of the membrane. The unit permeability of CO2 decreases with increasing pressure, further indicating the absence of viscous flow in the membrane. The pure H2 permeability remains constant with pressure due to the absence of defects and linear gas absorption ( Figure 15 The H2 permeability contributed by the STT molecular sieve channel exceeds 98% ( Figure 16 , Table 3). However, the pure CH4 permeability increases with increasing pressure up to 2.1 MPa, which is contrary to the theoretical downward trend derived from nonlinear adsorption behavior ( Figure 15 Because CH4 diffuses slowly in the STT channel, the non-zeolite pores become the primary transport pathway for CH4 permeation. Their contribution is 22% at 0.1 MPa, increasing to 52% at 2.1 MPa (Table 4).

[0083] Table 3 quantitatively analyzes the contribution of STT molecular sieve membrane to single H2 permeation based on SF6 permeation data, including Knudsen diffusion (P Knu ), viscous flow (P Vis ) and molecular sieve channels (P Zeo )

[0084]

[0085]

[0086] a: Measured at 298K;

[0087] b: ×10 -10 mol·m -2 ·s -1 ·Pa -1 .

[0088] Table 4 quantitatively analyzes the contribution of STT molecular sieve membrane to single CH4 permeation based on SF6 permeation data, including Knudsen diffusion (P Knu ), viscous flow (P Vis ) and molecular sieve channels (P Zeo )

[0089]

[0090] a: Measured at 298K;

[0091] b: ×10 -10 mol·m -2 ·s -1 ·Pa -1 .

[0092] H2 / CH4 separation performance under high pressure

[0093] Equimolar H2 / CH4 mixtures were used to determine the high pressure separation performance ( Figure 15 The H2 permeability and H2 / CH4 mixture selectivity at atmospheric pressure are 6.1×10 -8 mol·m -2 ·s -1 ·Pa -1 and 115. Even though similar trends were observed, the selectivity of H2 / CH4 mixtures was lower than that of the pure components. The slow-diffusing CH4 molecules greatly hindered the diffusion of H2 due to the stronger interaction (21.9 vs. 6.4 kJ·mol -1 , Table 5), CH4 molecules preferentially adsorbed in the STT cages. At 2.1 MPa, the selectivity of the H2 / CH4 mixture was still as high as 14% (Table 6), indicating that the H2 purity can be increased from 50% to 92.4% through a single-stage process. Even with only 35% H2 permeability retained, the flux of the H2 / CH4 mixture was as high as 2.0 Nm at 2.1 MPa. 3 ·m -2 ·h -1 ( Figure 15 At the same time, this value is twice that of DD3R molecular sieve membrane (2.4×10 -8 mol·m -2 ·s -1 ·Pa -1 vs1.1×10 -8 mol·m -2 ·s -1 ·Pa -1 ), which makes STT molecular sieve membranes more attractive for practical high-pressure H2 / CH4 separation.

[0094] Table 5 Langmuir adsorption parameters of STT molecular sieve membrane for H2 and CH4

[0095]

[0096] a: Fitted by the two-variable Langmuir equation.

[0097] Table 6 High-pressure H2 / CH4 membrane separation performance data

[0098]

[0099] In summary, STT zeolite membranes were hydrothermally synthesized on hollow fibers under static conditions by adjusting the water content. The in situ precursor transitioned from a liquid to a semisolid state, and nucleation in the bulk gel was effectively suppressed. The optimized STT zeolite membrane had a H2 permeability of 6.1×10 -8 mol·m -2 ·s -1 ·Pa -1 , H2 / CH4 selectivity is 115. Under 2.1MPa conditions, H2 / CH4 selectivity drops to 14, and the H2 flux is 2.0Nm 3 ·m -2 ·h -1 The use of the present invention to prepare STT molecular sieve membranes can significantly reduce chemical waste by 50%, which will pave the way for high-pressure H2 separation.

[0100] The above is only a preferred embodiment of the patent of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the patent of the present invention. These improvements and modifications should also be regarded as the scope of protection of the patent of the present invention.

Claims

1. A method for preparing STT molecular sieve membrane by static synthesis, characterized in that: The steps include: S1, coating SiO2 particles on the surface of the support and then calcining; S2, coating STT molecular sieve seed crystals on the surface of the calcined support; S3, placing the coated support in a synthesis liquid and performing hydrothermal synthesis under static conditions; the synthesis liquid after the reaction is semi-solid, and the molar ratio of the raw materials in the synthesis liquid is: 1SiO2: (0.1-0.3) TMAdaOH: (84-104) H2O; S4. After cleaning and drying, the template is removed by calcination in an ozone atmosphere.

2. The method for preparing STT molecular sieve membrane by static synthesis according to claim 1, characterized in that: In the step S1, the support body is made of alumina hollow fibers with multiple channels; The average pore size of the alumina hollow fiber is in the range of 50-500 nm, and the porosity is 20-50%; The calcination conditions are: 600-1000K, 6-10h.

3. The method for preparing STT molecular sieve membrane by static synthesis according to claim 1, characterized in that: In the step S2, the STT molecular sieve seed crystals are coated with an aqueous suspension containing 0.3-1.2 wt.% of small-particle-size STT molecular sieve seed crystals; The synthesis method of the small-particle STT molecular sieve seed crystals is as follows: SiO2, NaOH, Al(OH)3, TMAdaOH and H2O are mixed to obtain a mixed solution, and then the STT molecular sieve seed crystals are added to the mixed solution and hydrothermally crystallized to obtain the obtained solution; Wherein, in the mixed solution, the molar ratio of SiO2, NaOH, Al(OH)3, TMAdaOH and H2O is: 1:(0.1-0.3):(0.002-0.01):(0.1-0.5):(130-180); The mass concentration of STT molecular sieve seeds added to the mixed solution is 0.05-0.2wt.%; The conditions for hydrothermal crystallization are: 400-550K, 10-48h.

4. The method for preparing STT molecular sieve membrane by static synthesis according to claim 1, characterized in that: In the step S3, the static condition includes no rotation during the hydrothermal synthesis process; The conditions for hydrothermal synthesis are: 400-550K, 24-120h.

5. The method for preparing STT molecular sieve membrane by static synthesis according to claim 4, characterized in that: 0.001-0.15 wt.% of STT molecular sieve seeds are also added to the synthesis solution.

6. The method for preparing STT molecular sieve membrane by static synthesis according to claim 5, characterized in that: The molar ratio of raw materials in the synthetic liquid is 1SiO2:0.2TMAdaOH:84H2O.

7. The method for preparing STT molecular sieve membrane by static synthesis according to claim 1, characterized in that: In the step S4, the calcination conditions in the ozone atmosphere are: 450-500K, 48-100h.

8. A method for recycling a synthetic solution to repeatedly prepare an STT molecular sieve membrane, characterized in that: The method comprises recovering the synthetic liquid according to claim 7, adding 5-20 wt.% of TMAdaOH solution to the recovered synthetic liquid, and then preparing the STT molecular sieve membrane.

9. An STT molecular sieve membrane, characterized in that: The method is prepared by any one of claims 1 to 7.

10. Use of the STT molecular sieve membrane according to claim 9 in separating H2, characterized in that Used to separate H2 from H2 / CH4 mixed gas, operating pressure 0.1-2.8MPa.

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