A method for repairing a molecular sieve membrane

Abstract

The present application belongs to the field of molecular sieve membrane repair, and particularly relates to a method for repairing a molecular sieve membrane. The method uses NO2 and SO2 to repair the molecular sieve membrane. NO2 molecules are prone to dimerization to form N2O4 under certain conditions (low temperature or high pressure), and N2O4 can react with SO2 to form a complex ONONO-SO3, which can form strong affinity with the hydroxyl group exposed at the defect site of the molecular sieve membrane, thereby plugging the molecular sieve membrane channel and repairing the molecular sieve membrane. For small-pore molecular sieve membranes such as six-membered ring or eight-membered ring, N2O4 has a kinetic diameter greater than the pore diameter of the molecular sieve membrane, so it cannot enter the molecular sieve membrane channel and cause channel plugging. For ten-membered ring or twelve-membered ring molecular sieve membranes with larger pore diameters, the adsorption of the ONONO-SO3 complex is not strong due to the larger pore diameter of the molecular sieve membrane, and selective heating desorption can be selected, so the channel will not be permanently plugged.

Description

Technical Field

[0001] This invention belongs to the field of molecular sieve membrane repair, and specifically relates to a method for repairing molecular sieve membranes. Background Technology

[0002] Membrane separation technology, as one of the mainstream gas separation technologies in modern times, has broad application prospects in industrial product gas production, comprehensive utilization of waste gas, and environmental protection. Compared with other separation technologies, it has unique advantages: energy saving, no phase change, no secondary pollution, simple operation, compact structure, low maintenance cost, easy to scale up, and easy to automate.

[0003] Zeolite molecular sieve membranes, as an important member of inorganic porous membranes, possess advantages such as high temperature resistance, antimicrobial properties, good structural stability, and stable chemical properties. Furthermore, due to their pore structure, which is similar in size to most molecules, and their narrow pore size distribution and uniform channels, they exhibit selective separation of molecules with different kinetic diameters at the molecular scale, along with strong design flexibility and adaptability. An ideal molecular sieve membrane should be formed by highly cross-linked molecular sieve crystals, free of any defects, and achieve molecular sieving and adsorption through regular and uniform molecular sieve channels.

[0004] However, in actual molecular sieve membrane production, the synthesized molecular sieve membranes often fail to form a uniform, continuous, and dense membrane layer, which greatly reduces their separation performance. In actual membrane separation processes, due to factors such as the impact of the separated gas and corrosion, the lifespan of molecular sieve membranes is generally short, making it impossible to work continuously for a long time and reducing the economic benefits of membrane separation technology.

[0005] Molecular sieve membranes are polycrystalline membranes formed by the cross-linking and growth of zeolite crystals under hydrothermal conditions. Due to the poor intergrowth of zeolite crystals, intergranular pores (grain boundary defects) often form. Grain boundaries in molecular sieve membranes are inherent to the polycrystalline membrane itself and are difficult to eliminate; their presence significantly reduces the membrane's separation efficiency. While grain boundary defects are inherent to the polycrystalline membrane structure and cannot be completely eliminated, their size and density can be adjusted through secondary growth. However, this increases the membrane thickness, leading to a substantial reduction in permeate flux.

[0006] Therefore, reducing intercrystalline pore defects in molecular sieve membranes and timely repairing damaged molecular sieve membranes are crucial for improving the separation performance and economic benefits of molecular sieve membranes. Traditional methods for repairing defects in molecular sieve membranes (including coking and chemical deposition methods for repairing grain boundary defects) generally have the following drawbacks: (1) narrow range of defects that can be repaired; (2) inability to distinguish between defects and molecular sieve pores for effective selective repair, resulting in a significant reduction in the permeate flux of the repaired molecular sieve membrane; (3) some repair methods are complex and demanding, unsuitable for industrial scale-up, and have no industrial application value; (4) high energy consumption of the coking method; and (5) high cost of the chemical deposition method.

[0007] The application of molecular sieve membrane repair technology can reduce membrane production costs, extend the effective lifespan of molecular sieve membranes, and improve their applicability and reliability, thus ensuring the industrial application of zeolite molecular sieve membranes. Therefore, there is an urgent need to find a highly selective, low-cost, easy-to-operate, easily scaled-up industrial method for repairing defects in molecular sieve membranes of various defect types. Summary of the Invention

[0008] To address the aforementioned problems, this invention proposes a method for repairing molecular sieve membranes, which utilizes NO2 and SO2. NO2 molecules readily dimerize under certain conditions (low temperature or high pressure) to form N2O4. N2O4 reacts with SO2 to form the complex ONONO-SO3. This complex forms hydrogen bonds with exposed hydroxyl groups at defect sites in the molecular sieve membrane, thereby blocking the membrane pores and repairing it. Adding H2O promotes the oxidation reaction between NO2 and SO2 to generate SO3, lowering the activation energy required for the reaction and allowing it to participate in the formation of the more stable complex SO3-2HONO, thus strengthening the repair process. For six-membered and eight-membered ring molecular sieve membranes, due to the kinetic diameter of N2O4… For molecules larger than the pore diameter of the molecular sieve membrane, no hydroxyl groups will enter the pores, thus preventing pore blockage. For ten-membered ring molecular sieve membranes with larger pore diameters, since there are no exposed hydroxyl groups within the pores, the adsorption of the complexes formed in the reaction is weak, and therefore, pore blockage will not occur.

[0009] This invention is achieved through the following technical solution:

[0010] This invention proposes a method for repairing molecular sieve membranes. The method involves passing a first mixed gas containing NO2 and SO2 into the surface of the molecular sieve membrane for repair, cleaning off excess acidic substances from the repaired molecular sieve membrane, and then drying it to obtain the repaired molecular sieve membrane.

[0011] Furthermore, the method specifically includes: placing the cleaned molecular sieve membrane in a molecular sieve membrane fixing device, introducing the first mixed gas, the first mixed gas entering from the gas inlet end of the molecular sieve membrane fixing device, a portion permeating the molecular sieve membrane and exiting through the gas outlet end, and a portion exiting from the permeate end; the proportion of gas permeating the molecular sieve membrane depends on the pore size and defect degree of the molecular sieve membrane (the larger the size and the more defects, the more permeates), its function is to enter the defect pores of the molecular sieve membrane and form complexes; the permeate end is for venting excess NO2 and SO2, and the pressure difference between the two ends of the membrane can be controlled by adjusting the pressure reducing valve at the permeate end;

[0012] The molecular sieve membrane is dried to obtain the repaired molecular sieve membrane.

[0013] Furthermore, the specific steps for removing excess acidic substances from the repaired molecular sieve membrane include: placing the repaired molecular sieve membrane in a petri dish and immersing it thoroughly in 50ml of deionized water;

[0014] After a period of time (30-60 minutes), check the pH value of the deionized water in the petri dish. If the pH value is less than 7, replace the deionized water. Repeat the two steps of checking the pH value and replacing the deionized water until the pH value is equal to 7.

[0015] Furthermore, depending on the application environment of the molecular sieve membrane, the method further includes, after introducing the first mixed gas, sequentially introducing a second mixed gas and a third mixed gas onto the surface of the molecular sieve membrane; introducing the second mixed gas promotes the oxidation reaction between NO2 and SO2 to generate SO3, reduces the activation energy required for the reaction, and participates in the reaction to generate a more stable complex SO3-2HONO, thereby repairing the defective pores of the molecular sieve membrane; the reason for not introducing it simultaneously with SO2 and NO2 is to prevent them from reacting in the gas pipeline and clogging the pipeline; the purpose of introducing the second mixed gas is to form a more stable complex, and it should be selected according to the actual application of the subsequent molecular sieve membrane. For example, if the temperature of the subsequent molecular sieve membrane application scenario is higher than 850℃ and the pressure difference is greater than 10MPa, then the second mixed gas should be introduced.

[0016] Furthermore, after the second mixed gas is introduced, a third mixed gas needs to be introduced to react with the excess second mixed gas. The introduction of the third mixed gas specifically includes: closing the outlet end of the fixed device, and the third mixed gas containing NO2 and SO2 entering from the inlet end, passing through the molecular sieve membrane surface, and then being discharged from the permeate end.

[0017] Furthermore, the molecular sieve membrane is an inorganic membrane with a main pore size of less than 1.2 nm; specifically, it includes:

[0018] Ten-membered ring: MFI molecular sieve membrane, MEL molecular sieve membrane;

[0019] Eight-membered ring: AEI molecular sieve membrane, CHA molecular sieve membrane, LTA molecular sieve membrane, DDR molecular sieve membrane, RHO molecular sieve membrane, ERI molecular sieve membrane, AFX molecular sieve membrane, SFW molecular sieve membrane, RTH molecular sieve membrane, KFI molecular sieve membrane, ITE molecular sieve membrane, IHW molecular sieve membrane, ITW molecular sieve membrane, NSI molecular sieve membrane, LEV molecular sieve membrane, STT molecular sieve membrane;

[0020] Six-membered ring: SOD molecular sieve membrane.

[0021] Furthermore, the specific steps for cleaning the molecular sieve membrane include:

[0022] S1: Use tweezers to pick up the synthesized molecular sieve membrane and rinse the surface of the molecular sieve membrane with deionized water 2 to 5 times, each time for 1 to 3 minutes;

[0023] S2: Place the molecular sieve membrane in a petri dish and add deionized water until the molecular sieve membrane is submerged;

[0024] S3: Place the petri dish into an ultrasonic cleaner and ultrasonically clean for 30-60 seconds;

[0025] S4: Dry the molecular sieve membrane in an oven or muffle furnace at a temperature of 100-200℃.

[0026] S5: Place the molecular sieve membrane into the fixing device with the membrane surface facing the gas inlet end, and purge with dry N2 for 6 to 12 hours.

[0027] Furthermore, in the fixed device, the membrane surface of the molecular sieve membrane faces the air inlet end, and the pressure difference between the two ends of the membrane is 0.05 to 3 MPa.

[0028] Furthermore, the volume concentration of NO2 in the first mixed gas is 0.1-20%, the volume concentration of SO2 is 0.1-20%, and the remainder is N2.

[0029] Furthermore, before mixing NO2 and SO2, the flow rate of NO2 is 10-100 mL / min and the flow rate of SO2 is 10-100 mL / min. The first mixed gas obtained under this flow rate range can achieve the purpose of quickly reaching the pressure required for the reaction and repairing the molecular sieve membrane (flow rate greater than 10 mL / min), and can also protect the molecular sieve membrane from further damage caused by the impact of large flow rates (flow rate less than 100 mL / min).

[0030] Furthermore, the reaction temperature for the repair by introducing the first mixed gas is -50 to 200°C; preferably, at a reaction temperature of 20°C, based on the introduction of the first gas (5% volume concentration of SO2 and NO2, 0.1 MPa) for 2 hours, the N2 permeability is reduced by 94% and the CO2 / N2 separation coefficient is increased by 8.4 times after repair.

[0031] Furthermore, the first mixed gas is continuously introduced for 3 to 24 hours.

[0032] Furthermore, the gases and their volume concentrations in the second mixed gas include: 1-50% water vapor, with the remainder being N2.

[0033] Furthermore, the reaction temperature for the second mixed gas remediation is 20–100°C.

[0034] Furthermore, the second mixed gas is continuously introduced for 6 to 48 hours.

[0035] Furthermore, the volume concentrations of NO2 and SO2 in the third mixed gas are equal to or higher than the volume concentrations of NO2 and SO2 in the first mixed gas by 1% to 5%; the flow rates are equal to or higher than the flow rates of NO2 and SO2 in the first mixed gas by 1 to 10 mL / min; the remainder is N2.

[0036] Furthermore, the reaction temperature for the repair by introducing the third mixed gas is -50 to 200°C.

[0037] Furthermore, the third mixed gas is continuously introduced for 6 to 36 hours.

[0038] Furthermore, the specific steps of drying the molecular sieve membrane include: placing the repaired molecular sieve membrane in a 100°C oven for 1 hour, or using a microwave drying method; the purpose is to remove water molecules adsorbed in the crystal channels of the molecular sieve membrane, and then storing it at a constant temperature of 60-80°C (for example, storing it in a 60-80°C oven).

[0039] Furthermore, after the first mixed gas enters the defective pores of the molecular sieve membrane, a second mixed gas is introduced to react and further repair the pores; then a third mixed gas is introduced, enters the defective pores of the molecular sieve membrane, and reacts with excess water molecules to further repair the molecular sieve membrane (because water molecules have a strong adsorption capacity, there is often excessive adsorption when the second mixed gas is introduced).

[0040] The method for repairing molecular sieve membranes described in this invention has the following beneficial technical effects:

[0041] 1) The present invention uses a mixed gas of NO2 and SO2 to reduce grain boundary defects in the molecular sieve membrane without increasing the membrane thickness, and thus without reducing the permeation flux of the molecular sieve membrane.

[0042] This invention uses a mixture of NO2 and SO2 gases to repair defects in molecular sieve membranes. The NO2 and SO2 mixture reacts at the defect sites in the molecular sieve membrane, blocking the defect channels and improving the integrity of the membrane, thereby enhancing its separation performance for the separation system.

[0043] 2) This invention can be used to repair molecular sieve membranes damaged by corrosion, impact, etc. in practical applications. The method is simple and low-cost, which can effectively extend the working life of molecular sieve membranes and thus improve the economic benefits of membrane separation technology.

[0044] 3) This invention can be carried out at room temperature, which greatly reduces the energy consumption of the molecular sieve membrane repair process.

[0045] 4) NO2 and SO2 are two common pollutants in industry. This invention can realize the full utilization of recovered NO2 and SO2.

[0046] 5) Based on the appropriate molecular diameters of NO2 and SO2, the NO2-SO2 repair method can effectively repair intercrystalline defects. Compared with traditional repair methods, it has lower energy consumption and lower cost. Attached Figure Description

[0047] Figure 1 This is a schematic diagram of the molecular sieve membrane fixing device in an embodiment of the present invention.

[0048] Figure 2 This is a schematic diagram of the molecular sieve membrane repair experimental apparatus in an embodiment of the present invention.

[0049] Figure 3 This is a comparison of the CO2 / N2 separation coefficients of the molecular sieve membrane before and after repair, based on the first mixed gas (5% volume concentration of SO2 and NO2, at room temperature of 20°C and 0.1 MPa) in Example 2 of the present invention.

[0050] Explanation of reference numerals in the attached diagram: 1-Outlet end, 2-Molecular sieve membrane, 3-Inlet end, 4-Permeate end, 5-Water vapor cylinder, 6-Nitrogen cylinder, 7-Nitrogen dioxide cylinder, 8-Sulfur dioxide cylinder, 9-Flow controller, 10-Coil, 11-Pressure measuring instrument, 12-Molecular sieve membrane fixing device, 13-Water bath / oil bath, 14-Decompression valve, 15-Tail gas treatment device. Detailed Implementation

[0051] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0052] Conversely, this invention covers any substitutions, modifications, equivalent methods, and schemes made within the spirit and scope of the invention as defined by the claims. Furthermore, to provide the public with a better understanding of the invention, certain specific details are described in detail below. However, those skilled in the art will fully understand the invention even without these detailed descriptions.

[0053] The following examples illustrate the function of the invention. In these examples, unless otherwise stated, parts are calculated by weight, percentages are calculated by weight percentage, and temperatures are in degrees Celsius. The relationship between fractions by weight and parts by volume is the same as the relationship between grams and cubic centimeters.

[0054] Example 1

[0055] This embodiment proposes a method for repairing molecular sieve membranes, referring to... Figure 1 and Figure 2 The method involves passing a first mixed gas containing NO2 and SO2 into the surface of a molecular sieve membrane for repair, cleaning off excess acidic substances from the repaired molecular sieve membrane, and then drying it to obtain the repaired molecular sieve membrane.

[0056] The method specifically includes: placing the cleaned molecular sieve membrane in a molecular sieve membrane fixing device, introducing the first mixed gas, the first mixed gas entering from the gas inlet end of the molecular sieve membrane fixing device, part of which permeates through the molecular sieve membrane and exits through the gas outlet end, and part of which exits from the permeate end; the proportion of gas permeating through the molecular sieve membrane depends on the pore size and defect degree of the molecular sieve membrane (the larger the size and the more defects, the more permeates), its function is to enter the defect pores of the molecular sieve membrane and form complexes; the permeate end is for the discharge of excess NO2 and SO2, and the pressure difference between the two ends of the membrane can be controlled by adjusting the pressure reducing valve at the permeate end;

[0057] The molecular sieve membrane is dried to obtain the repaired molecular sieve membrane.

[0058] The specific steps for removing excess acidic substances from the repaired molecular sieve membrane include: placing the repaired molecular sieve membrane in a petri dish and immersing it thoroughly in 50ml of deionized water.

[0059] After a period of time (30-60 minutes), check the pH value of the deionized water in the petri dish. If the pH value is less than 7, replace the deionized water. Repeat the two steps of checking the pH value and replacing the deionized water until the pH value is equal to 7.

[0060] Depending on the application environment of the molecular sieve membrane, the method further includes, after introducing the first mixed gas, sequentially introducing a second mixed gas and a third mixed gas onto the surface of the molecular sieve membrane; introducing the second mixed gas promotes the oxidation reaction between NO2 and SO2 to generate SO3, reduces the activation energy required for the reaction, and participates in the reaction to generate a more stable complex SO3-2HONO, thereby repairing the defective pores of the molecular sieve membrane; the reason for not introducing it simultaneously with SO2 and NO2 is to prevent them from reacting in the gas pipeline and clogging the pipeline; the purpose of introducing the second mixed gas is to form a more stable complex, and it should be selected according to the actual application of the subsequent molecular sieve membrane. For example, if the temperature of the subsequent molecular sieve membrane application scenario is higher than 850℃ and the pressure difference is greater than 10MPa, then the second mixed gas should be introduced.

[0061] After the second mixed gas is introduced, a third mixed gas needs to be introduced to react with the excess second mixed gas. The introduction of the third mixed gas specifically includes: closing the outlet end of the fixed device, and the third mixed gas containing NO2 and SO2 entering from the inlet end, passing through the molecular sieve membrane surface, and then being discharged from the permeate end.

[0062] The molecular sieve membrane is an inorganic membrane with a main pore size of less than 1.2 nm; specifically, it includes:

[0063] Ten-membered ring: MFI molecular sieve membrane, MEL molecular sieve membrane;

[0064] Eight-membered ring: AEI molecular sieve membrane, CHA molecular sieve membrane, LTA molecular sieve membrane, DDR molecular sieve membrane, RHO molecular sieve membrane, ERI molecular sieve membrane, AFX molecular sieve membrane, SFW molecular sieve membrane, RTH molecular sieve membrane, KFI molecular sieve membrane, ITE molecular sieve membrane, IHW molecular sieve membrane, ITW molecular sieve membrane, NSI molecular sieve membrane, LEV molecular sieve membrane, STT molecular sieve membrane;

[0065] Six-membered ring: SOD molecular sieve membrane.

[0066] The specific steps involved in cleaning the molecular sieve membrane include:

[0067] S1: Use tweezers to pick up the synthesized molecular sieve membrane and rinse the surface of the molecular sieve membrane with deionized water 2 to 5 times, each time for 1 to 3 minutes;

[0068] S2: Place the molecular sieve membrane in a petri dish and add deionized water until the molecular sieve membrane is submerged;

[0069] S3: Place the petri dish into an ultrasonic cleaner and ultrasonically clean for 30-60 seconds;

[0070] S4: Dry the molecular sieve membrane in an oven or muffle furnace at a temperature of 100-200℃.

[0071] S5: Place the molecular sieve membrane into the fixing device with the membrane surface facing the gas inlet end, and purge with dry N2 for 6 to 12 hours.

[0072] The molecular sieve membrane is positioned in a fixed device with its surface facing the inlet end, and the pressure difference between the two ends of the membrane is 0.05–3 MPa.

[0073] The volume concentration of NO2 in the first mixed gas is 0.1-20%, the volume concentration of SO2 is 0.1-20%, and the remainder is N2.

[0074] Before mixing NO2 and SO2, the NO2 flow rate is 10-100 mL / min and the SO2 flow rate is 10-100 mL / min. The first mixed gas obtained under this flow rate range can achieve the required pressure for the reaction more quickly and achieve the purpose of repairing the molecular sieve membrane (flow rate greater than 10 mL / min), while also protecting the molecular sieve membrane from further damage caused by the impact of large flow rates (flow rate less than 100 mL / min).

[0075] The reaction temperature for the repair by introducing the first mixed gas is -50 to 200°C; preferably, at a reaction temperature of 20°C, based on the introduction of the first gas (5% volume concentration of SO2 and NO2, 0.1 MPa) for 2 hours, the N2 permeability is reduced by 94% and the CO2 / N2 separation coefficient is increased by 8.4 times after repair.

[0076] The first mixed gas is continuously introduced for 3 to 24 hours.

[0077] The gases and their volume concentrations in the second mixed gas include: water vapor 1-50%, with the remainder being N2.

[0078] The reaction temperature for the second mixed gas repair is 20–100°C.

[0079] The second mixed gas is continuously introduced for 6 to 48 hours.

[0080] The volume concentrations of NO2 and SO2 in the third mixed gas are equal to or higher than those in the first mixed gas by 1% to 5%; the flow rates are equal to or higher than those in the first mixed gas by 1 to 10 mL / min; the remainder is N2.

[0081] The reaction temperature for the repair by introducing the third mixed gas is -50 to 200°C.

[0082] The third mixed gas is continuously introduced for 6 to 36 hours.

[0083] The specific steps of drying the molecular sieve membrane include: placing the repaired molecular sieve membrane in a petri dish or plastic box; then placing it in an oven at a temperature of 60-80℃; the purpose of storing it in the oven is to use the higher temperature to evaporate the water molecules adsorbed in the crystal channels of the molecular sieve membrane.

[0084] After the first mixed gas enters the defective pores of the molecular sieve membrane, the second mixed gas is introduced to react and further repair the pores; then the third mixed gas is introduced, enters the defective pores of the molecular sieve membrane, and reacts with excess water molecules to further repair the molecular sieve membrane (because water molecules have a strong adsorption capacity, there is often excessive adsorption when the second mixed gas is introduced).

[0085] In this embodiment, following the method described above, CO2 / CH4 is first separated using a synthesized, dense CHA molecular sieve membrane, with a CO2 permeability of 2.5 × 10⁻⁶. -7 mol·m -2 ·Pa -1 ·s -1 The CH4 permeability is 5.9 × 10⁻⁶. -9 mol·m -2 ·Pa -1 ·s -1 The initial separation coefficient was 42.4; after 600 hours of continuous separation, the CO2 permeability decreased to 2.8 × 10⁻⁶ due to damage to the molecular sieve membrane. -7 mol·m -2 ·Pa -1 ·s -1 CH4 permeability increased to 4.2 × 10⁻⁶ -8 mol·m -2 ·Pa -1 ·s -1 The separation coefficient was reduced to 6.7; using the method of this embodiment to repair the molecular sieve membrane, the repaired molecular sieve membrane achieved a CO2 / CH4 separation coefficient of 45, and a CO2 permeability of 2.3 × 10⁻⁶. -7 mol·m -2 ·Pa -1 ·s -1 CH4 permeability is 5.9 × 10⁻⁶ -9 mol·m -2 ·Pa -1 ·s -1 .

[0086] Example 2

[0087] In this embodiment, only the first mixed gas is introduced to repair the defective CHA molecular sieve membrane after synthesis. It has virtually no separation capability for CO2 / N2, with a CO2 permeability of 2.79 × 10⁻⁶. -7 mol·m -2 ·Pa -1·s -1 The N2 permeability is 2.37 × 10⁻⁶. - 7 mol·m -2 ·Pa -1 ·s -1 The molecular sieve membrane was repaired using the method described in Example 1, and the CO2 permeability after repair was 1.56 × 10⁻⁶. -7 mol·m -2 ·Pa -1 ·s -1 N2 penetration decreased to 1.61 × 10⁻⁶ -8 mol·m -2 ·Pa -1 ·s -1 The separation coefficient increased to 9.67, such as Figure 3 As shown.

[0088] Example 3

[0089] In this embodiment, the MFI molecular sieve membrane with defects after synthesis was repaired. Before repair, the separation coefficient of the MFI molecular sieve membrane for n- / isobutane at 185°C was 9.7, and after repair, the separation coefficient was increased to 107.

[0090] Example 4

[0091] In this embodiment, the MFI molecular sieve membrane with defects after synthesis was repaired. Before repair, the separation coefficient of the MFI molecular sieve membrane for para / o-xylene at 400°C was 4.7, and after repair, the separation coefficient was increased to 32.5.

[0092] Example 5

[0093] This embodiment uses only the first mixed gas to repair the defective STT molecular sieve membrane after synthesis. Before repair, the N2 permeability was 1.07 × 10⁻⁶. -7 mol·m -2 ·Pa -1 ·s -1 CH4 permeability is 8.42 × 10⁻⁶ -8 mol·m -2 ·Pa -1 ·s -1 The separation coefficient was 1.27; the N2 permeability after repair was 8.90 × 10⁻⁶. -8 mol·m -2 ·Pa -1 ·s -1 The CH4 permeability is 8.89 × 10⁻⁶. -7 mol·m -2 ·Pa -1 ·s -1 The separation coefficient is 10.

[0094] Example 6

[0095] This embodiment repairs a defective SOD molecular sieve membrane after synthesis and performs H2 / CH4 separation tests. Before repair, the H2 permeability was 4.52 × 10⁻⁶. -8 mol·m -2 ·Pa -1 ·s -1 CH4 permeability is 2.71 × 10⁻⁶ -8 mol·m -2 ·Pa -1 ·s -1 The separation coefficient was 1.67; the H2 permeability after repair was 4.21 × 10⁻⁶. -8 mol·m -2 ·Pa -1 ·s -1 CH4 permeability is 5.66 × 10⁻⁶ - 9 mol·m -2 ·Pa -1 ·s -1 The separation coefficient was 7.44.

[0096] Example 7

[0097] This embodiment repairs a defective LTA molecular sieve membrane after synthesis. Before repair, the N2 permeability was 1.88 × 10⁻⁶. - 7 mol·m -2 ·Pa -1 ·s -1 CH4 permeability is 7.69 × 10⁻⁶ -8 mol·m -2 ·Pa -1 ·s -1 The separation coefficient was 2.44; the H2 permeability after repair was 4.21 × 10⁻⁶. -8 mol·m -2 ·Pa -1 ·s -1 CH4 permeability is 5.66 × 10⁻⁶ -9 mol·m -2 ·Pa -1 ·s -1 The separation coefficient was 7.44.

[0098] Example 8

[0099] In this embodiment, a defective CHA molecular sieve membrane was repaired after synthesis. Before repair, the N2 permeability was 1.07 × 10⁻⁶. - 7 mol·m -2 ·Pa -1 ·s -1CO2 permeability is 1.59 × 10⁻⁶ -8 mol·m -2 ·Pa -1 ·s -1 The separation coefficient was 1.49, indicating that it had virtually no separation capability; the N2 permeability after repair was 9.25 × 10⁻⁶. -9 mol·m -2 ·Pa -1 ·s -1 CO2 permeability is 1.23 × 10⁻⁶ -7 mol·m -2 ·Pa -1 ·s -1 The separation coefficient was 13.3. After 168 hours of separation under a pressure difference of 12 MPa, the separation coefficient remained unchanged.

Claims

1. A method for repairing molecular sieve membranes, characterized in that, The method involves passing a first mixed gas containing NO2 and SO2 into the surface of a molecular sieve membrane for repair, removing excess acidic substances from the repaired molecular sieve membrane, and then drying it to obtain the repaired molecular sieve membrane. The molecular sieve membrane is positioned with its surface facing the inlet end in a fixed device, and the pressure difference between the two ends of the membrane is 0.05~3MPa. The volume concentration of NO2 in the first mixed gas is 1~50%, the volume concentration of SO2 is 1~50%, and the remainder is N2; The reaction temperature for the repair by introducing the first mixed gas is -50~200℃.

2. The method for repairing a molecular sieve membrane according to claim 1, characterized in that, The molecular sieve membrane is an inorganic membrane with a main pore size of less than 1.2 nm; comprising: Ten-membered ring: MFI molecular sieve membrane, MEL molecular sieve membrane; Eight-membered ring: AEI molecular sieve membrane, CHA molecular sieve membrane, LTA molecular sieve membrane, DDR molecular sieve membrane, RHO molecular sieve membrane, ERI molecular sieve membrane, AFX molecular sieve membrane, SFW molecular sieve membrane, RTH molecular sieve membrane, KFI molecular sieve membrane, ITE molecular sieve membrane, IHW molecular sieve membrane, ITW molecular sieve membrane, NSI molecular sieve membrane, LEV molecular sieve membrane, STT molecular sieve membrane; Six-membered ring: SOD molecular sieve membrane.

3. The method for repairing a molecular sieve membrane according to claim 1, characterized in that, The method specifically includes: placing the cleaned molecular sieve membrane in a molecular sieve membrane fixing device, introducing the first mixed gas, the first mixed gas entering from the gas inlet end of the molecular sieve membrane fixing device, a portion of which permeates through the molecular sieve membrane and is discharged through the gas outlet end, and a portion of which is discharged from the permeate end. The molecular sieve membrane is dried to obtain the repaired molecular sieve membrane.

4. The method for repairing a molecular sieve membrane according to claim 2, characterized in that, Depending on the application environment of the molecular sieve membrane, the method further includes, after introducing the first mixed gas, sequentially introducing a second mixed gas and a third mixed gas onto the surface of the molecular sieve membrane.

5. The method for repairing a molecular sieve membrane according to claim 4, characterized in that, The gases and their volume concentrations in the second mixed gas include: water vapor 1-50%, with the remainder being N2.

6. The method for repairing a molecular sieve membrane according to claim 4, characterized in that, The reaction temperature for the second mixed gas repair is 20~100℃.

7. A method for repairing a molecular sieve membrane according to claim 1 or 2, characterized in that, The specific steps of drying the molecular sieve membrane include: drying the repaired molecular sieve membrane in an oven or using microwave drying; and then storing it at a constant temperature of 60-80℃.

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