Synthesis system and synthesis method of molecular sieve membrane

Abstract

The invention provides a synthesis system and a synthesis method of a molecular sieve membrane, the synthesis system comprises a reaction liquid storage tank, a long barrel type reaction kettle and a reaction liquid recovery tank, an outlet of the reaction liquid storage tank is connected with a feed port of the long barrel type reaction kettle, and a discharge port of the long barrel type reaction kettle is connected with the reaction liquid recovery tank; wherein the reaction liquid storage tank and the long barrel type reaction kettle are respectively provided with a temperature control device; a molecular sieve membrane support body is arranged in the long barrel type reaction kettle along the axial direction, and the ratio of the size of the molecular sieve membrane support body along the radial direction of the reaction kettle to the diameter of the reaction kettle is 1: (1.01-5). The preparation time of the molecular sieve membrane with the specific thickness is shortened, meanwhile, the defect that the molecular sieve membrane is uneven in thickness is overcome, and the molecular sieve membrane with the uniform thickness and the uniform compactness is prepared.

Description

A synthesis system and method for molecular sieve membranes Technical Field

[0001] This invention relates to the field of molecular sieve membrane preparation technology, and specifically to a molecular sieve membrane synthesis system and synthesis method. Background Technology

[0002] Molecular sieves possess controllable pore structures, adjustable and uniform pore sizes, with pore sizes closely resembling molecular dimensions. Due to their unique pore structure, molecular molecules can selectively permeate through them. Membrane materials made from molecular sieves selectively pass molecules with kinetic diameters smaller than the sieve pore diameter based on their molecular size, thus separating substances through molecular-size sieving. Molecular sieves are generally made from silicon-aluminum materials; different silicon-to-aluminum ratios result in different polarities. Molecular sieves with specific polarities can selectively adsorb molecules with corresponding dipole moments, allowing these molecules to then permeate the membrane. Therefore, molecular sieve membranes can separate substances based on polarity differences. Compared to organic polymer membrane materials, inorganic molecular sieve membrane materials exhibit relatively higher hydrothermal stability, relatively higher molecular permeability and separation selectivity, and lack a Robeson upper limit. The permeability and selectivity of molecular sieve membranes can be improved through modification and alteration, making them a promising separation material for industrial applications.

[0003] SAPO-34 molecular sieves possess an eight-membered ring three-dimensional pore structure with pore sizes of 0.36 × 0.36 nm, close to the kinetic diameter of most gas molecules. Its molecular sieve membrane can separate gas molecules through sieving. Furthermore, SAPO-34 molecular sieves have a polarity close to that of CO2, exhibiting a strong adsorption capacity for CO2. Therefore, it can simultaneously utilize polarity to separate CO2 molecules from N2, H2, He, and CH4 molecules, demonstrating high separation selectivity. Consequently, SAPO-34 molecular sieve membranes have long been the preferred material for CO2 separation.

[0004] However, the synthesis time of SAPO-34 molecular sieve membranes is relatively long, requiring tens of hours or even several days. Studies have found that microwave heating can shorten the synthesis time of SAPO-34 molecular sieves by 5 to 10 hours, but microwave heating is difficult to implement industrially. The literature (L.Bai,N.Chang,M.Li,Y.Wang,G.Nan,Y.Zhang,D.Hu,G.Zeng,W.Wei,Ultrafast synthesis of thin SAPO-34zeolite membrane by oil-bathheating,Microporous and MesoporousMaterials(2017),doi:10.1016 / j.micromeso.2016.12.019.) uses oil bath heating, which can shorten the reaction time to about 1 hour, but the reaction temperature used is relatively high, and the molecular sieve membranes prepared at this temperature are uneven in thickness and have many defects. Summary of the Invention

[0005] To address the aforementioned technical problems, the present invention aims to provide a molecular sieve membrane synthesis system and synthesis method.

[0006] To achieve the above objectives, the present invention provides a molecular sieve membrane synthesis system, comprising: a reaction solution storage tank, a long barrel-shaped reaction vessel, and a reaction solution recovery tank, wherein the outlet of the reaction solution storage tank is connected to the inlet of the long barrel-shaped reaction vessel, and the outlet of the long barrel-shaped reaction vessel is connected to the reaction solution recovery tank.

[0007] The reaction liquid storage tank and the long barrel-shaped reaction vessel are each equipped with a temperature control device;

[0008] The long barrel-shaped reactor is provided with a molecular sieve membrane support along the axial direction. The ratio of the radial dimension of the molecular sieve membrane support to the diameter of the reactor is 1:1.01-5, more preferably 1.01-2 times.

[0009] The synthesis system of this invention can promptly pump fresh reaction solution (with constant concentration of each component) into a long barrel-shaped reactor, eliminating the concentration gradient of the solution; the size design of the reactor can eliminate the temperature gradient, allowing the reactor to instantly reach the synthesis temperature; based on the combination of the above designs, this invention greatly shortens the preparation time of molecular sieve membranes of a specific thickness while overcoming the defect of uneven thickness of molecular sieve membranes, and produces molecular sieve membranes with uniform thickness and fewer defects.

[0010] The synthesis system of this invention differs from microwave heating methods and is easily implemented in industry.

[0011] In the aforementioned molecular sieve membrane synthesis system, preferably, a feed pump is installed on the pipeline between the outlet of the reaction liquid storage tank and the inlet of the long barrel-shaped reactor. More preferably, the feed pump and / or discharge pump are equipped with metering devices for quantitatively pumping the liquid.

[0012] In the aforementioned molecular sieve membrane synthesis system, preferably, the reaction solution storage tank is also equipped with a stirring device. The reaction solution storage tank, equipped with both a heating device and a stirring device, preheats the reaction solution, which helps to reduce the temperature difference of the reaction solution film within the reactor. The heating device of the long-barrel-shaped reactor further ensures that the reaction temperature remains within the set range and guarantees uniform temperature within the reactor.

[0013] In the above-mentioned molecular sieve membrane synthesis system, preferably, a shut-off valve is provided on the pipeline between the discharge port of the long barrel-shaped reactor and the reaction liquid recovery tank to maintain the pressure inside the reactor.

[0014] In the above-mentioned molecular sieve membrane synthesis system, preferably, the reaction solution storage tank and the reaction solution recovery tank are the same tank.

[0015] In the above-mentioned molecular sieve membrane synthesis system, preferably, there is a gap between the molecular sieve membrane support and the side wall of the long barrel-shaped reactor, and the axial direction of the molecular sieve membrane support is parallel to the axial direction of the long barrel-shaped reactor.

[0016] According to a specific embodiment of the present invention, preferably, the diameters of the long barrel-shaped reactor and the molecular sieve membrane support are 10-500 mm.

[0017] According to a specific embodiment of the present invention, preferably, the molecular sieve membrane support is disposed on the central axis of the long barrel-shaped reactor.

[0018] According to a specific embodiment of the present invention, preferably, the molecular sieve membrane support is disposed at the middle position of the axial direction of the long barrel-shaped reactor.

[0019] According to a specific embodiment of the present invention, preferably, the long barrel-shaped reactor is arranged horizontally or vertically.

[0020] According to a specific embodiment of the present invention, preferably, the elongated cylindrical reactor includes a vessel body, with end caps at both ends of the vessel body, wherein at least one end cap is a detachable end cap. This facilitates the loading and unloading of the molecular sieve membrane support.

[0021] According to a specific embodiment of the present invention, preferably, the detachable end cap is connected to the long barrel-shaped reactor by threads, nuts, bolts or snap fasteners.

[0022] According to a specific embodiment of the present invention, preferably, the inner side of the end cap is provided with a support fixing structure for detachably fixing each molecular sieve membrane support.

[0023] According to a specific embodiment of the present invention, preferably, the support fixing structure is a protrusion or a groove. When the support fixing structure is a protrusion, the protrusion corresponds to the inner diameter of the molecular sieve support; for a single-channel support, it is an independent single protrusion, and for a multi-channel support, it is a plurality of protrusions of corresponding number. When the support fixing structure is a groove, the groove is a fully enclosed circular ring structure or a semi-enclosed arc structure.

[0024] According to a specific embodiment of the present invention, preferably, the molecular sieve membrane support is a tubular support or a plate support. More preferably, the tubular support is a single-tube support or a multi-channel support.

[0025] According to a specific embodiment of the present invention, preferably, the molecular sieve membrane support is made of ceramic, metal or organic polymer material.

[0026] According to a specific embodiment of the present invention, preferably, the molecular sieve membrane synthesis system is used to synthesize SAPO-34 molecular sieve membranes.

[0027] According to a specific embodiment of the present invention, preferably, the inner ends of the elongated cylindrical reactor, excluding the edges, are provided with structures for fixing molecular sieve membrane supports. These supports are arranged opposite to each other, making the supports parallel to the sides of the reactor and creating a certain gap between the supports and the inner wall of the reactor. The structures for fixing the molecular sieve membrane supports are grooves or protrusions. The structures for fixing the molecular sieve membrane supports can be positioned near the center at both ends of the reactor, or they can be positioned near or off-center at both ends of the reactor.

[0028] The present invention also provides a method for synthesizing a molecular sieve membrane, which is carried out using the above-mentioned molecular sieve membrane synthesis system, and the synthesis method includes the following steps:

[0029] The molecular sieve membrane support is seeded to obtain a seeded support, which is then placed in a long barrel-shaped reactor.

[0030] Inject the film-forming solution into the reaction solution storage tank and preheat it to the reaction temperature;

[0031] The long barrel-shaped reactor is heated to the reaction temperature, and then the membrane-forming solution in the reaction solution storage tank is continuously transported to the inlet of the long barrel-shaped reactor for hydrothermal reaction. The pressure of the long barrel-shaped reactor is controlled by the shut-off valve. The reaction solution after the reaction is simultaneously output to the reaction solution recovery tank, and a molecular sieve membrane is obtained on the molecular sieve membrane support.

[0032] In the above-mentioned method for synthesizing molecular sieve membranes, preferably, the seed crystals on the molecular sieve membrane support are SAPO-34 molecular sieves.

[0033] In the above-mentioned method for synthesizing molecular sieve membranes, preferably, the pressure of the long barrel-shaped reactor is 0.01-1 MPa, more preferably 0.02-0.4 MPa.

[0034] In the above-mentioned method for synthesizing molecular sieve membranes, preferably, the hydrothermal reaction temperature is 180-250℃ and the reaction time is 5-24h.

[0035] In the above-mentioned method for synthesizing molecular sieve membranes, preferably, the input rate of the membrane-forming solution in the long barrel-shaped reactor is 0.01-5 L / min, more preferably 0.01-1 L / min.

[0036] In the above-mentioned method for synthesizing molecular sieve membranes, preferably, the seeded support is prepared by the following method:

[0037] A suspension of molecular sieve seed crystals is coated onto the surface of a support and dried at 80-150°C for 5-24 hours to obtain the seeded support; wherein the concentration of molecular sieve seed crystals in the suspension is 0.5-3 wt%. More preferably, the solvent of the molecular sieve seed crystal suspension is water and / or ethanol.

[0038] In the above-mentioned method for synthesizing molecular sieve membranes, preferably, the raw materials of the membrane-forming solution include silicon source, aluminum source, phosphoric acid, template agent and water, and the molar ratio of silicon source, aluminum source, phosphoric acid, template agent and water based on oxides is (0.6-0.8):(0.9-1.1):(0.8-1):(1-8):(50-260), that is, n(SiO2):n(Al2O3):n(P2O5):n(template agent):n(H2O)=(0.6-0.8):(0.9-1.1):(0.8-1):(1-8):(50-260).

[0039] In the above-mentioned method for synthesizing molecular sieve membranes, preferably, the template agent includes at least one of tetraethylammonium hydroxide, triethylamine, and morpholine.

[0040] In the above-mentioned method for synthesizing molecular sieve membranes, preferably, the preparation method of the membrane-forming solution is as follows: aluminum source is added to water, then phosphoric acid is added and stirred until a colloid is formed, then silicon source and template agent are added, and the mixture is stirred and aged to obtain the membrane-forming solution. More preferably, the stirring time during the process of adding phosphoric acid to form a colloid is 0.5-2 hours; the stirring and aging time after adding silicon source and template agent is 3-10 hours.

[0041] In the above-mentioned method for synthesizing molecular sieve membranes, preferably, the method further includes: after the reaction is completed, removing the seeded support, and calcining the seeded support in a segmented manner under a nitrogen or ozone atmosphere to remove the template agent, thereby obtaining the molecular sieve membrane on the surface of the support.

[0042] In the above-mentioned method for synthesizing molecular sieve membranes, preferably, the segmented calcination includes two stages of calcination. The calcination temperature of the first stage is 300-600℃, and the calcination time is 1-6h. The calcination temperature of the second stage is 400-800℃, which is higher than the calcination temperature of the first stage, and the calcination time is 1-6h.

[0043] In the above-mentioned method for synthesizing molecular sieve membranes, preferably, the heating rate to the calcination temperature of each stage is 0.5-10℃.

[0044] The technical solution provided by this invention has the following beneficial effects:

[0045] In this invention, the reaction solution is dynamically pumped into a long, cylindrical reactor, ensuring that all reaction solutions in contact with the molecular sieve membrane support are fresh. Simultaneously, the reactor diameter is close to the radial dimension of the support, reducing the temperature gradient and allowing the area around the support to quickly reach the molecular sieve membrane synthesis temperature. This combination of designs reduces the synthesis time for molecular sieve membranes of a certain thickness. The constant composition and uniform reaction temperature of the reaction solution at the support surface result in a molecular sieve membrane with uniform thickness and density. Attached Figure Description

[0046] Figure 1 shows the synthesis system of the SAPO-34 molecular sieve membrane in Example 1;

[0047] Figure 2 shows the structure of the long barrel-shaped reactor of the synthesis system in Example 1;

[0048] Figure 3 shows the structure when the support fixing structure on the end cap is protruding;

[0049] Figure 4 shows the structure when the support fixing structure on the end cap is a slot;

[0050] Figure 5 shows the structure of the SAPO-34 molecular sieve membrane synthesis system (containing multiple reaction vessels) of Example 2;

[0051] Figure 6 shows the structure of the long barrel-shaped reactor of the synthesis system in Example 3;

[0052] Figure 7 shows the structure of the long barrel-shaped reactor (with detachable ends) of the synthesis system in Example 4;

[0053] Figure 8 shows the structure of the long barrel-shaped reactor of the synthesis system in Example 5;

[0054] Figure 9 shows the structure of the long barrel-shaped reactor of the synthesis system in Example 6;

[0055] Figure 10 shows the structure of the long barrel-shaped reactor (one end is detachable) of the synthesis system in Example 7;

[0056] Figure 11a is a cross-sectional electron microscope image of the molecular sieve membrane prepared in Example 11;

[0057] Figure 11b is a surface electron microscope image of the molecular sieve membrane prepared in Example 11;

[0058] Figure 12a is a cross-sectional electron microscope image of the molecular sieve membrane prepared in Comparative Example 2;

[0059] Figure 12b is a surface electron microscope image of the molecular sieve membrane prepared in Comparative Example 2;

[0060] Figure 13 is a surface electron microscope image of the molecular sieve membrane prepared in Comparative Example 3;

[0061] Figure 14 shows the surface electron microscope image of the molecular sieve membrane prepared in Comparative Example 4.

[0062] Explanation of icon numbers:

[0063] 1. Long barrel-shaped reactor; 2. Reaction liquid storage tank; 3. Reaction liquid recovery tank; 4. Pumping device; 5. Shut-off valve.

[0064] 1-1. Feed inlet; 1-2. Discharge outlet; 1-3. End cap; 1-4. Molecular sieve membrane support; 1-5. Support fixing structure; 1-6. Kettle body; 2-1. Stirring device. Detailed Implementation

[0065] In order to provide a clearer understanding of the technical features, objectives and beneficial effects of the present invention, the technical solution of the present invention will now be described in detail below, but it should not be construed as limiting the scope of implementation of the present invention.

[0066] Example 1

[0067] This embodiment provides a synthesis system for SAPO-34 molecular sieve membranes, as shown in Figure 1, which includes: a long barrel-shaped reactor 1, a reaction liquid storage tank 2, a reaction liquid recovery tank 3, a feed pump 4, and a shut-off valve 5;

[0068] The long barrel-shaped reactor 1 is provided with an inlet 1-1, an outlet 1-2, and an end cap 1-3. The outlet of the reaction liquid storage tank 2 is connected to the inlet 1-1 of the long barrel-shaped reactor 1, and the outlet 1-2 of the long barrel-shaped reactor 1 is connected to the reaction liquid recovery tank 3. The reaction liquid storage tank 2 and the long barrel-shaped reactor 1 are respectively provided with temperature control devices, and the reaction liquid storage tank 2 is also provided with a stirring device 2-1. A molecular sieve membrane support 1-4 is fixed axially inside the long barrel-shaped reactor 1. The ratio of the radial dimension of the molecular sieve membrane support 1-4 to the diameter of the reactor is 1:1.01.

[0069] A metering feed pump 4 is installed on the pipeline between the outlet of the reaction liquid storage tank 2 and the inlet 1-1 of the long barrel-shaped reactor 1, and a shut-off valve 5 is installed on the pipeline between the outlet 1-2 of the long barrel-shaped reactor 1 and the reaction liquid recovery tank 3.

[0070] As shown in Figure 2, a tubular molecular sieve membrane support 1-4 is located at the center of the central axis inside the long barrel-shaped reactor 1. A gap exists between the molecular sieve membrane support 1-4 and the side wall of the long barrel-shaped reactor 1. The axial direction of the molecular sieve membrane support 1-4 is parallel to the axial direction of the long barrel-shaped reactor 1. The diameter of the long barrel-shaped reactor 1 is 1.01 times that of the molecular sieve membrane support 1-4 (the diameter of the long barrel-shaped reactor is 505 mm, and the diameter of the molecular sieve membrane support is 500 mm). The long barrel-shaped reactor 1 includes a reactor body 1-6, with end caps 1-3 at both ends. One end cap 1-3 is detachable for loading and unloading the molecular sieve membrane support 1-4. The molecular sieve membrane support 1-4 is located at the center of the axis of the long barrel-shaped reactor 1.

[0071] The inner side of the end cap 1-3 of the long barrel-shaped reactor 1 is provided with a support fixing structure 1-5 for detachably fixing the molecular sieve membrane support 1-4; the support fixing structure 1-5 is a protrusion (as shown in Figure 3) or a groove (as shown in Figure 4).

[0072] Example 2

[0073] This embodiment provides a synthesis system for SAPO-34 molecular sieve membranes, which is the same as that in Embodiment 1, except that, as shown in Figure 5, the long barrel-shaped reactor 1 is designed as multiple reactors (the diameter of the long barrel-shaped reactor is 20 mm, and the diameter of the molecular sieve membrane support is 10 mm). The three reactors are connected in parallel. The feed inlet 1-1 is located at one end of the reactor, allowing simultaneous feeding to all three reactors; the discharge outlet 1-2 is located at the other end of the reactor, allowing simultaneous discharge of the liquid from all three reactors. A common removable end cap 1-3 is provided at the end of the reactor near the feed inlet, allowing the molecular sieve membrane support 1-4 to be inserted into the reactor body.

[0074] Example 3

[0075] This embodiment provides a synthesis system for SAPO-34 molecular sieve membranes, which is the same as that in Embodiment 1, except that, as shown in Figure 6, the long barrel-shaped reactor 1 is provided with multiple molecular sieve membrane supports 1-4 inside, and the end caps at both ends of the long barrel-shaped reactor are detachable end caps.

[0076] Example 4

[0077] This embodiment provides a synthesis system for SAPO-34 molecular sieve membranes, which is the same as that in Embodiment 1, except that, as shown in Figure 7, the end caps at both ends of the long barrel-shaped reactor 1 are detachable end caps 1-3, and the diameter of the long barrel-shaped reactor 1 is 5 times that of the molecular sieve membrane support 1-4 (the diameter of the long barrel-shaped reactor is 50 mm, and the diameter of the molecular sieve membrane support is 10 mm).

[0078] Example 5

[0079] This embodiment provides a synthesis system for SAPO-34 molecular sieve membranes, which is the same as that in Embodiment 1, except that, as shown in Figure 8, no support structure is provided inside the long barrel-shaped reactor 1, and the end caps 1-3 at both ends of the long barrel-shaped reactor are detachable end caps.

[0080] Example 6

[0081] This embodiment provides a synthesis system for SAPO-34 molecular sieve membranes, which is the same as that in Embodiment 1, except that, as shown in Figure 9, the molecular sieve membrane support 1-4 is not positioned in the middle of the axial direction of the long barrel-shaped reactor 1.

[0082] Example 7

[0083] This embodiment provides a synthesis system for SAPO-34 molecular sieve membranes, which is the same as that in Embodiment 1, except that, as shown in Figure 10, no support structure is provided inside the long barrel-shaped reactor 1, and the molecular sieve membrane supports 1-4 are not located in the middle of the axial direction of the long barrel-shaped reactor.

[0084] Example 8

[0085] This embodiment provides a method for synthesizing SAPO-34 molecular sieve membranes, which is carried out using the synthesis system of Example 1. In this synthesis system, the molecular sieve membrane support 1-4 is a four-pore tubular support.

[0086] The synthesis method in this embodiment includes the following steps:

[0087] (1) Preparation of film-forming solution:

[0088] Weigh out boehmite, silica sol, phosphoric acid, triethylamine (TEA) template agent, and deionized water in the following proportions, with a molar ratio of n(SiO2):n(Al2O3):n(P2O5):n(TEA):n(H2O) = 0.6:1:0.8:3:60; add boehmite to deionized water, add phosphoric acid dropwise while stirring, stir for 1 hour, add silica sol and triethylamine template agent, and continue stirring for 8 hours to obtain the film-forming solution;

[0089] (2) Preparation of seeded support:

[0090] 10g of SAPO-34 molecular sieve seed crystals with an average particle size of 2μm were weighed and dispersed in 990g of deionized water. The solution was placed in a seed crystal container with a stirrer and stirred for 10h. Then, the solution was sonicated for 30min to obtain a SAPO-34 molecular sieve seed crystal suspension. A four-hole tubular support was immersed in the seed crystal suspension. After 1min, the support was removed and placed in an oven at 80℃ for 24h to obtain a seeded support.

[0091] (3) Hydrothermal reaction:

[0092] The seeded support obtained in step (2) is placed into the long barrel-shaped reactor of Example 1 and fixed with the support fixing structure, and the end cap is closed; then the film-forming solution obtained in step (1) is added to the reaction solution storage tank, the stirring device and the heating device are turned on, and the film-forming solution is heated to 200°C; then the long barrel-shaped reactor is heated to 200°C, the feed pump is turned on, the flow rate of the film-forming solution (reaction solution) is 0.10 mL / min, the reaction solution is continuously pumped and hydrothermally reacted at 200°C for 10 h, and the pressure inside the long barrel-shaped reactor is controlled to be 0.08 MPa by the shut-off valve, and the reaction solution flows out to the reaction solution recovery tank;

[0093] (4) Take the film:

[0094] After the hydrothermal reaction is completed, the support is removed, rinsed with deionized water and dried, and then heated to 400°C at a rate of 1°C / min under a nitrogen atmosphere and calcined for 2 hours. Then, the temperature is increased to 600°C at a rate of 1°C / min and calcined for 4 hours to remove the template agent, thus obtaining the SAPO-34 molecular sieve membrane.

[0095] Example 9

[0096] This embodiment provides a method for synthesizing SAPO-34 molecular sieve membranes, which is carried out using the synthesis system of Example 4, wherein a three-porous tubular support is used for the molecular sieve support.

[0097] The synthesis method in this embodiment includes the following steps:

[0098] (1) Preparation of film-forming solution:

[0099] Weigh out boehmite, silica sol, phosphoric acid, tetraethylammonium hydroxide (TEAOH) template agent, and deionized water in the following proportions, with a molar ratio of n(SiO2):n(Al2O3):n(P2O5):n(TEAOH):n(H2O) = 0.8:1.1:1:8:260; add boehmite to deionized water, add phosphoric acid dropwise while stirring, stir for 3 hours, add silica sol and tetraethylammonium hydroxide template agent, and continue stirring for 10 hours to obtain the film-forming solution;

[0100] (2) Preparation of seeded support:

[0101] 10g of SAPO-34 molecular sieve seed crystals with an average particle size of 2μm were weighed and dispersed in 990g of deionized water. The solution was placed in a seed crystal container with a stirrer and stirred for 10h. Then, the solution was sonicated for 30min to obtain a SAPO-34 molecular sieve seed crystal suspension. A four-hole tubular support was immersed in the seed crystal suspension. After 1min, the support was removed and placed in an oven at 150℃ for 6h to obtain a seeded support.

[0102] (3) Hydrothermal reaction:

[0103] The seeded support obtained in step (2) is placed into the long barrel-shaped reactor of Example 4 and fixed with the support fixing structure, and the end cap is closed; then the film-forming liquid obtained in step (1) is added to the reaction liquid storage tank, the stirring device and the heating device are turned on, the film-forming liquid is heated to 250°C, then the long barrel-shaped reactor is heated to 250°C, the liquid pumping device is turned on, the flow rate of the film-forming liquid (reaction liquid) is 0.30 mL / min, the reaction liquid is continuously pumped and hydrothermally reacted at 250°C for 5 hours, and the pressure inside the long barrel-shaped reactor is controlled to be 0.4 MPa by the shut-off valve, while the reaction liquid flows out to the reaction liquid recovery tank;

[0104] (4) Take the film:

[0105] After the hydrothermal reaction was completed, the support was removed, rinsed with deionized water, and dried. Then, under an ozone atmosphere, the temperature was increased to 350°C at a rate of 3°C / min and calcined for 2 hours. Next, the temperature was increased to 500°C at a rate of 3°C / min and calcined for 4 hours to remove the template agent, thus obtaining the SAPO-34 molecular sieve membrane.

[0106] Example 10

[0107] This embodiment provides a method for synthesizing SAPO-34 molecular sieve membranes, which is carried out using the synthesis system of Example 6, wherein a six-pore tubular support is used as the molecular sieve support.

[0108] The synthesis method in this embodiment includes the following steps:

[0109] (1) Preparation of film-forming solution:

[0110] Weigh out boehmite, silica sol, phosphoric acid, deionized water, and tetraethylammonium hydroxide (TEAOH) in the following proportions, with a molar ratio of n(SiO2):n(Al2O3):n(P2O5):n(TEAOH):n(H2O) = 0.6:0.9:0.8:5:200. Add boehmite to deionized water, and while stirring, add phosphoric acid dropwise. Stir for 3 hours, then add silica sol and tetraethylammonium hydroxide template agent and continue stirring for 10 hours to obtain the film-forming solution.

[0111] (2) Preparation of seeded support:

[0112] 10g of SAPO-34 molecular sieve seed crystals with an average particle size of 2μm were weighed and dispersed in 990g of deionized water. The solution was placed in a seed crystal container with a stirrer and stirred for 10h. Then, the solution was sonicated for 30min to obtain a SAPO-34 molecular sieve seed crystal suspension. A four-hole tubular support was immersed in the seed crystal suspension. After 1min, the support was removed and placed in an oven at 150℃ for 6h to obtain a seeded support.

[0113] (3) Hydrothermal reaction:

[0114] The seeded support obtained in step (2) is placed into the long barrel-shaped reactor of Example 6 and fixed with the support fixing structure, and the end cap is closed; then the film-forming liquid obtained in step (1) is added to the reaction liquid storage tank, the stirring device and the heating device are turned on, the film-forming liquid is heated to 190°C, and then the long barrel-shaped reactor is heated to 190°C. The liquid pumping device is turned on, the flow rate of the film-forming liquid (reaction liquid) is 10mL / min, and the reaction liquid is continuously pumped to perform hydrothermal reaction at 190°C for 10h. The pressure inside the long barrel-shaped reactor is controlled to be 0.2MPa by the shut-off valve, and the reaction liquid flows out to the reaction liquid recovery tank.

[0115] (4) Take the film:

[0116] After the hydrothermal reaction is completed, the support is removed, rinsed with deionized water and dried, and then heated to 350°C at a rate of 2°C / min under an ozone atmosphere and calcined for 4 hours. Then, the temperature is increased to 600°C at a rate of 2°C / min and calcined for 2 hours to remove the template agent, thus obtaining the SAPO-34 molecular sieve membrane.

[0117] Example 11

[0118] This embodiment provides a method for synthesizing SAPO-34 molecular sieve membranes, which is carried out using the synthesis system of Example 5, wherein a single-pore tubular support is used as the molecular sieve support.

[0119] (1) Preparation of film-forming solution:

[0120] Weigh out boehmite, silica sol, phosphoric acid, TEAOH+TEA template agent (mass ratio 1:2), and deionized water in the following proportions, with a molar ratio of n(SiO2):n(Al2O3):n(P2O5):n(template agent):n(H2O) = 0.6:1:0.8:1.5:80. Add boehmite to deionized water, and while stirring, add phosphoric acid dropwise. Stir for 1 hour, then add silica sol and TEAOH+TEA template agent and continue stirring for 8 hours to obtain the film-forming solution.

[0121] (2) Preparation of seeded support:

[0122] 10g of SAPO-34 molecular sieve seed crystals with an average particle size of 2μm were weighed and dispersed in 990g of deionized water. The solution was placed in a seed crystal container with a stirrer and stirred for 10h. After sonication for 30min, a SAPO-34 molecular sieve seed crystal suspension was obtained. A four-hole tubular support was immersed in the seed crystal suspension. After 1min, the support was removed and placed in an oven at 100℃ for 12h to obtain a seeded support.

[0123] (3) Hydrothermal reaction:

[0124] The seeded support obtained in step (2) is placed into the long barrel-shaped reactor of Example 5 and fixed with the support fixing structure, and the end cap is closed; then the film-forming liquid obtained in step (1) is added to the reaction liquid storage tank, the stirring device and the heating device are turned on, the film-forming liquid is heated to 180°C, and then the long barrel-shaped reactor is heated to 180°C. The liquid pumping device is turned on, the flow rate of the film-forming liquid (reaction liquid) is 1L / min, and the reaction liquid is continuously pumped to perform hydrothermal reaction at 180°C for 14h. The pressure inside the long barrel-shaped reactor is controlled to be 0.2MPa by the shut-off valve, and the reaction liquid flows out to the reaction liquid recovery tank.

[0125] (4) Take the film:

[0126] After the hydrothermal reaction is completed, the support is removed, rinsed with deionized water and dried, and then heated to 400°C at a rate of 2°C / min under a nitrogen atmosphere and calcined for 2 hours. Then, the temperature is increased to 550°C at a rate of 2°C / min and calcined for 3 hours to remove the template agent, thus obtaining the SAPO-34 molecular sieve membrane.

[0127] Example 12

[0128] This embodiment provides a method for synthesizing SAPO-34 molecular sieve membrane, which is the same as that in Example 8, except that the synthesis method in this embodiment is implemented using the synthesis system of Example 2, and the molecular sieve support in the device is a single-pore tubular support.

[0129] Example 13

[0130] This embodiment provides a method for synthesizing SAPO-34 molecular sieve membranes, which is carried out using the synthesis system of Example 2, wherein a single-pore tubular support is used as the molecular sieve support.

[0131] The preparation method of the film-forming solution in this embodiment is as follows:

[0132] (1) Preparation of film-forming solution:

[0133] Weigh out aluminum triethanolamine, silica sol, phosphoric acid, TEAOH template agent, and deionized water in the following proportions, with a molar ratio of n(SiO2):n(Al2O3):n(P2O5):n(TEAOH):n(H2O) = 0.6:1:0.8:3:80. Add aluminum triethanolamine to deionized water, and while stirring, add phosphoric acid dropwise. Stir for 1 hour, then add silica sol and TEAOH template agent and continue stirring for 8 hours to obtain the film-forming solution.

[0134] (2) Preparation of seeded support:

[0135] 10g of SAPO-34 molecular sieve seed crystals with an average particle size of 2μm were weighed and dispersed in 990g of deionized water. The solution was placed in a seed crystal container with a stirrer and stirred for 10h. Then, the solution was sonicated for 30min to obtain a SAPO-34 molecular sieve seed crystal suspension. A four-hole tubular support was immersed in the seed crystal suspension. After 1min, the support was removed and placed in an oven at 110℃ for 10h to obtain a seeded support.

[0136] (3) Hydrothermal reaction:

[0137] The seeded support obtained in step (2) is placed into the long barrel-shaped reactor of Example 2 and fixed with the support fixing structure, and the end cap is closed; then the film-forming liquid obtained in step (1) is added to the reaction liquid storage tank, the stirring device and the heating device are turned on, the film-forming liquid is heated to 180°C, and then the long barrel-shaped reactor is heated to 180°C. The liquid pumping device is turned on, the flow rate of the film-forming liquid (reaction liquid) is 500mL / min, and the reaction liquid is continuously pumped to perform hydrothermal reaction at 180°C for 10h. The pressure inside the long barrel-shaped reactor is controlled to be 0.2MPa by the shut-off valve, and the reaction liquid flows out to the reaction liquid recovery tank.

[0138] (4) Take the film:

[0139] After the hydrothermal reaction is completed, the support is removed, rinsed with deionized water and dried, and then heated to 400°C at a rate of 2°C / min under a nitrogen atmosphere and calcined for 2 hours. Then, the temperature is increased to 550°C at a rate of 2°C / min and calcined for 3 hours to remove the template agent, thus obtaining the SAPO-34 molecular sieve membrane.

[0140] Comparative Example 1

[0141] This comparative example provides a method for synthesizing SAPO-34 molecular sieve membrane, which is the same as that in Example 13, except that step (3) is different.

[0142] Step (3) of this comparative example is as follows:

[0143] The seeded molecular sieve membrane support was placed in a conventional molecular sieve membrane reactor (the reactor has an internal diameter of 100 mm, the support has an external diameter of 10 mm, and the reactor diameter is 10 times that of the support), placed upright, and the reaction membrane solution was added so that the membrane solution submerged the support. The end caps were tightened, and the reactor was placed upright in an oven and reacted at 200°C for 48 h.

[0144] Comparative Example 2

[0145] This comparative example provides a method for synthesizing SAPO-34 molecular sieve membrane, which is the same as that in Example 13, except that step (3) is different.

[0146] Step (3) of this comparative example is as follows:

[0147] The seeded molecular sieve membrane support was placed in a conventional molecular sieve membrane reactor (the reactor has an internal diameter of 80 mm, the support has an external diameter of 10 mm, and the reactor diameter is 8 times that of the support), placed upright, and the reaction membrane solution was added so that the membrane solution submerged the support. The end caps were tightened, and the reactor was placed upright in an oven and reacted at 200°C for 12 hours.

[0148] Comparative Example 3

[0149] This comparative example provides a method for synthesizing SAPO-34 molecular sieve membrane, which is the same as that in Example 13, except that step (4) is different.

[0150] Step (4) of this comparative example is as follows:

[0151] After the hydrothermal reaction is completed, the support is removed, rinsed with deionized water and dried, and then heated to 400°C at a rate of 2°C / min in air and calcined for 2 hours. Then, the temperature is increased to 550°C at a rate of 2°C / min and calcined for 3 hours to remove the template agent, thus obtaining the SAPO-34 molecular sieve membrane.

[0152] Comparative Example 4

[0153] This comparative example provides a method for synthesizing SAPO-34 molecular sieve membrane, which is the same as that in Example 13, except that step (4) is different.

[0154] Step (4) of this comparative example is as follows:

[0155] After the hydrothermal reaction is completed, the support is removed, rinsed with deionized water and dried, and then rapidly heated to 400°C within 10 minutes under a nitrogen atmosphere and calcined for 2 hours. Then, the temperature is rapidly increased to 550°C within 5 minutes and calcined for 3 hours to remove the template agent, thus obtaining the SAPO-34 molecular sieve membrane.

[0156] Figures 11a and 11b are cross-sectional electron microscope images and surface electron microscope images of the molecular sieve membrane prepared in Example 11, respectively. It can be seen that the molecular sieve membrane has a uniform cross-section and surface distribution and a relatively thin thickness.

[0157] Figures 12a and 12b are cross-sectional electron microscope images and surface electron microscope images of the molecular sieve membrane prepared in Comparative Example 2, respectively. It can be seen that the surface thickness of the molecular sieve membrane is uneven.

[0158] Figure 13 is a surface electron microscope image of Comparative Example 3, in which no molecular sieve crystals were observed on the surface of the membrane.

[0159] Figure 14 is a surface electron microscope image of Comparative Example 4. It can be seen that the calcination of the tubular membrane caused cracks in the molecular sieve membrane.

[0160] The SAPO-34 molecular sieve membranes prepared in the above examples and comparative examples were tested for their permeability and selectivity to carbon dioxide and methane. The results are shown in Table 1, where CO2 / CH4 selectivity is the ratio of CO2 permeability to CH4 permeability.

[0161] Table 1. Permeability and selectivity of SAPO-34 molecular sieve membranes

[0162]

[0163]

[0164] As can be seen from Table 1, the SAPO-34 molecular sieve membrane synthesized in the embodiments of the present invention has high CO2 and CH4 permeability, and high CO2 / CH4 selectivity.

[0165] In Examples 8-12, the CO2 and CH4 permeability was higher than that in Comparative Examples 1-4. This is because the molecular sieve membranes synthesized in Examples 8-12 were relatively thin, which facilitates the permeation of gas molecules. Higher permeability can increase the throughput of the molecular sieve membrane per unit time. Furthermore, Table 1 shows that the CO2 / CH4 selectivity in Examples 8-12 was significantly higher than that in Comparative Examples 1-4. This is because the molecular sieve membranes in these examples were more regular and continuous, and this structure facilitates the selective separation of the two gases.

[0166] In Comparative Example 2, the permeability of the two gases was extremely high, but the selectivity was poor. This is because no molecular sieve crystals were generated in Comparative Example 2 within a conventional crystallization reactor and a relatively short synthesis time. No molecular sieve membrane was formed on the support, and the gases could permeate without resistance. Therefore, there was no separation selectivity between the two gases.

[0167] The higher transmittance and lower selectivity of Comparative Examples 3 and 4 are due to the fact that during the molecular sieve membrane extraction process, calcination or rapid heating in an air atmosphere can cause cracks in the molecular sieve membrane, damaging its structure and affecting the CO2 / CH4 selectivity.

Claims

1. A system for synthesizing molecular sieve membranes, comprising: The reactor comprises a reaction liquid storage tank, a long barrel-shaped reactor, and a reaction liquid recovery tank. The outlet of the reaction liquid storage tank is connected to the inlet of the long barrel-shaped reactor, and the outlet of the long barrel-shaped reactor is connected to the reaction liquid recovery tank. The reaction liquid storage tank and the long barrel-shaped reactor are each equipped with a temperature control device. A molecular sieve membrane support is provided axially inside the long barrel-shaped reactor, and the ratio of the radial dimension of the molecular sieve membrane support to the diameter of the reactor is 1:1.01-5.

2. The molecular sieve membrane synthesis system according to claim 1, wherein, A feed pump is installed on the pipeline between the outlet of the reaction liquid storage tank and the inlet of the long barrel-shaped reactor.

3. The molecular sieve membrane synthesis system according to claim 1, wherein, The reaction liquid storage tank is also equipped with a stirring device.

4. The molecular sieve membrane synthesis system according to claim 1, wherein, A shut-off valve is installed on the pipeline between the discharge port of the long barrel-shaped reactor and the reaction liquid recovery tank.

5. The molecular sieve membrane synthesis system according to claim 1, wherein, The reaction solution storage tank and the reaction solution recovery tank are the same tank.

6. The molecular sieve membrane synthesis system according to claim 1, wherein, There are one or more long barrel-shaped reactors; multiple long barrel-shaped reactors are connected in parallel.

7. The molecular sieve membrane synthesis system according to claim 1, wherein, There is a gap between the molecular sieve membrane support and the side wall of the long barrel-shaped reactor, and the axial direction of the molecular sieve membrane support is parallel to the axial direction of the long barrel-shaped reactor.

8. The molecular sieve membrane synthesis system according to claim 1, wherein, The molecular sieve membrane support is positioned on the central axis of the long barrel-shaped reactor.

9. The molecular sieve membrane synthesis system according to claim 1, wherein, The long barrel-shaped reactor can be installed horizontally or vertically.

10. The molecular sieve membrane synthesis system according to claim 1, wherein, The long barrel-shaped reactor is equipped with end caps, at least one of which is a detachable end cap; the inner side of the end cap is provided with a support structure for fixing.

11. A method for synthesizing a molecular sieve membrane, which is implemented using the molecular sieve membrane synthesis system according to any one of claims 1-10, the synthesis method comprising the following steps: seeding a molecular sieve membrane support to obtain a seeded support, and then placing it in a long barrel-shaped reactor and fixing it; injecting a membrane-forming solution into a reaction solution storage tank and preheating it to the reaction temperature; heating the long barrel-shaped reactor to the reaction temperature, and then continuously conveying the membrane-forming solution in the reaction solution storage tank to the long barrel-shaped reactor for hydrothermal reaction, and controlling the pressure of the long barrel-shaped reactor through a shut-off valve; simultaneously outputting the reaction solution after reaction to a reaction solution recovery tank, and obtaining a molecular sieve membrane on the molecular sieve membrane support.

12. The method for synthesizing molecular sieve membranes according to claim 11, wherein, The seed crystals on the molecular sieve membrane support are SAPO-34 molecular sieves.

13. The method for synthesizing the molecular sieve membrane according to claim 11, wherein, The pressure of the long barrel-shaped reactor is 0.01-1 MPa.

14. The method for synthesizing the molecular sieve membrane according to claim 11, wherein, The hydrothermal reaction temperature is 180-250℃, and the reaction time is 5-24h.

15. The method for synthesizing the molecular sieve membrane according to claim 11, wherein, The input rate of the film-forming solution in the long barrel-shaped reactor is 0.01-5 L / min.

16. The method for synthesizing molecular sieve membranes according to claim 11, wherein, The seeded support is prepared by coating a suspension of molecular sieve seeds onto the surface of the support and drying it at 80-150℃ for 5-24 hours to obtain the seeded support; wherein the concentration of molecular sieve seeds in the suspension is 0.5-3wt%.

17. The method for synthesizing molecular sieve membranes according to claim 11, wherein, The raw materials for the film-forming solution include silicon source, aluminum source, phosphoric acid, template agent and water. The molar ratio of silicon source, aluminum source, phosphoric acid, template agent and water (calculated as oxides) is (0.6-0.8):(0.9-1.1):(0.8-1):(1-8):(50-260).

18. The method for synthesizing molecular sieve membranes according to claim 17, wherein, An aluminum source is added to water, then phosphoric acid is added and stirred until a colloid is formed. A silicon source and a template agent are then added, and the mixture is stirred and aged to obtain the film-forming solution.

19. The method for synthesizing the molecular sieve membrane according to claim 17, wherein, The method for synthesizing molecular sieve membranes also includes: after the reaction is completed, the seeded support is removed, and the seeded support is subjected to segmented calcination in a nitrogen or ozone atmosphere to remove the template agent, and the molecular sieve membrane is obtained on the surface of the support.

20. The method for synthesizing a molecular sieve membrane according to claim 19, wherein, The segmented roasting includes two roasting stages. The roasting temperature of the first stage is 300-600℃, and the roasting time is 1-6h. The roasting temperature of the second stage is 400-800℃, which is higher than the roasting temperature of the first stage, and the roasting time is 1-6h.

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