WO2021104338A1 - Method of synthesizing molecular sieve membrane by employing successive generations - Google Patents

Abstract

A method of synthesizing a molecular sieve membrane by employing successive generations comprises a step of precoating with a crystal seed, in which a residual reaction liquid obtained from a crystallization reaction is used as a crystal seed solution to coat a support.

Description

Subsequent synthesis method of molecular sieve membrane Technical field

The invention relates to the technical field of membrane separation, in particular to the process of preparing molecular sieve membranes by a secondary growth method.

Background technique

Compared with traditional separation technology, membrane separation technology has the advantages of low energy consumption, less pollution, and convenient operation, which has attracted wide attention from academic and industrial circles (AIChE Journal, 50(10): 2326-2334). However, due to the production cost of molecular sieve membranes, the market potential of membrane separation technology has not been fully released. The synthesis cost of molecular sieve membranes mainly comes from the carrier and the synthesis process. In the prior art, the common synthesis methods of molecular sieve membranes mainly include in-situ growth method, solid phase transfer method and secondary growth method. The in-situ growth method places the carrier directly in the synthetic sol, and under suitable crystallization conditions, the molecular sieve is directly grown on the carrier to form a film. The process is simple and does not require a seed coating step, which is beneficial to the large-scale production of molecular sieve membranes. However, molecular sieve membranes synthesized by a single in-situ growth method often have a large number of defects, and the in-situ growth process needs to be repeated multiple times to ensure the separation performance of the membrane, which leads to an increase in production costs. Although the microwave technology combined with the in-situ growth method greatly reduces the number of repeated synthesis, more than two hydrothermal synthesis processes are still the basic requirements for preparing molecular sieve membranes that meet industrial application standards. The solid phase transfer method first introduces the seed gel layer on the carrier, and then places it in a reactor containing water or template agent, without direct contact with water or template agent, heating to vaporize the liquid while making the gel layer Crystallizes under the action of steam. This method can effectively control the amount of water and template agent, but due to the lack of fluidity of the synthetic system, it leads to more membrane defects, which is not conducive to industrial-scale production and application. The secondary growth method usually adopts the following steps: firstly, the seed crystal is pre-coated on the surface of the carrier, and then the carrier coated with the seed crystal is immersed in the synthetic sol, and the molecular sieve membrane is obtained by hydrothermal synthesis. The existence of seed crystals greatly shortens the nucleation induction period, which makes the molecular sieve preferentially grow on the surface of the carrier, which is conducive to the synthesis of dense molecular sieve membranes. However, this synthesis method has higher requirements for the seed layer, and requires uniform seed crystal size and uniform coating. Ultrasound assistance is often required during the preparation of the seed liquid, and the repeatability and accuracy in actual operation are difficult to control. In production applications, not only the process flow is increased, but also the coating equipment and seed crystal synthesis equipment have high requirements, which leads to a further increase in production costs. These characteristics severely limit the breadth and depth of its application in industrial production.

In view of this, the development of a stable, high-efficiency, energy-saving, and low-cost synthesis method for the synthesis of high-performance molecular sieve membranes is still an extremely challenging subject.

Summary of the invention

The purpose of the present invention is to provide a new process for the preparation of molecular sieve membranes based on the seeding method (secondary growth method). The new process should be able to make full use of the advantages of the existing technology and should be able to integrate the existing technology. Adjustments to make it more convenient, economical, environmentally friendly and smooth in industrial applications.

To this end, the present invention discloses a subsequent synthesis method of molecular sieve membranes, including the step of pre-coating seed crystals. The pre-coating seed crystals use the reaction residue after the crystallization reaction as the seed solution coating carrier. process.

The present invention is based on the technical solution of synthesizing molecular sieve membranes by the seed method in the prior art, and the method usually includes the steps of coating seed crystals and crystallization reaction. The inventor of the present application found that after the synthesis of the molecular sieve membrane, the remaining reaction liquid of the crystallization reaction contains a large number of small molecular sieve crystals, and through experiments, it has been found that the reaction residual liquid containing the small molecular sieve crystals can be used as a new one. Round synthetic seed liquid is used. And this simple operation scheme not only effectively realizes the recycling of the reaction residual liquid, greatly improves the utilization rate of materials, but also omits the process of preparing the seed liquid, and greatly reduces the cost of raw materials and procedures. However, it has been proved through multiple successive synthesis experiments that the molecular sieve membrane product prepared by the synthetic method of the present invention has excellent performance, low cost, good reproducibility of the preparation method, environmental friendliness, and great industrial application potential.

Description of the drawings

Figure 1 is the X-ray diffraction pattern of product 3;

Figure 2 is the X-ray diffraction pattern of products 16-19;

Figure 3 is the scanning electron microscope photos of products 16-19, where as, bs, cs, ds are the surface electron microscope scan photos of products 16-19, respectively, and ac, bc, cc, dc are the cross-sectional electron microscope scans of products 16-19, respectively photo;

Figure 4 is the scanning electron microscope photos of products 20, 22, 24, 26, 28, where as, bs, cs, ds, es are the surface electron microscope scanning photos of products 20, 22, 24, 26, 28, ac, bc , Cc, dc, and ec are the cross-sectional electron microscope scan photos of products 20, 22, 24, 26, and 28, respectively.

Figure 5 is the X-ray diffraction spectrum of products A1, A5, A10, B1, B5, B10, C5, C10, D5, and D10.

Figure 6 is the front and cross-sectional scanning electron micrographs of products A1, A5, A10, B1, B5, B10, C5, C10, D5, and D10.

Figure 7 is the X-ray diffraction spectrum of products G1 to G10.

Detailed ways

The present invention is based on the prior art of preparing molecular sieve membranes by the seed method, and provides a new method including material reuse and program integration. The core feature of the method lies in the reuse of the remaining liquid after the crystallization reaction, specifically using it as a seed liquid for a new round of molecular sieve membrane synthesis.

The method of the present invention includes the step of pre-coating seed crystals, which is a process of coating the carrier with the reaction residue after the crystallization reaction as the seed liquid, so as to obtain the carrier supporting the seed layer (also referred to as the composite I in this specification). ).

The method of the present invention can be described as a sustainable generation process. The method includes an N-generation synthesis process, where N is a positive integer; wherein the N-generation synthesis process includes the following steps:

When N=1, the carrier supporting the seed layer is placed in the reaction sol, and the first-generation molecular sieve membrane is prepared through the crystallization reaction; the reaction remaining liquid is used as the seed liquid for the second-generation synthesis process;

When N≥2: ①Pre-coated seed crystals: use the remaining liquid after the N-1 generation crystallization reaction as seed crystal liquid, uniformly coat the carrier, and let the coated carrier stand at room temperature until it is completely dry , Get the carrier supporting the seed layer; ② place the carrier supporting the seed layer in the reaction sol for crystallization reaction; ③ separate the molecular sieve membrane and the reaction residual liquid, (the molecular sieve membrane is washed to neutral, and dried) to obtain the Nth Generation molecular sieve membrane; the reaction residual liquid is used as the seed liquid of the N+1th generation synthesis process.

In the above technical solution of the present invention, theoretically the seed layer-supporting carrier in the first-generation synthesis process is prepared by any method in the existing methods. In a more preferred embodiment, the carrier supporting the seed layer in the first-generation synthesis process can be prepared using a seed solution coating method, and the seed solution used in the first-generation synthesis process is referred to as the first generation in this specification. Seed liquid. A suitable primary seed liquid is an important basis for the continuous and stable preparation of multi-generation molecular sieve membranes by the secondary synthesis method of the present invention, which can be prepared by any method in the prior art, such as the molecular sieve crystal grinding and dispersion method. However, it should be ensured that the first generation seed liquid and the reaction residue after the Nth generation reaction (ie the seed liquid of the N+1 generation reaction) have the same/similar characteristics, including the size, content, and sol group of the contained molecular sieve crystals. Sub-composition, concentration, etc. In the present invention, the following scheme is further preferably used: when N=1, the first-generation seed liquid is obtained by crystallization reaction of the reaction sol. The reaction sol mentioned herein has the same composition as the reaction sol used in the Nth generation synthesis process, and the crystallization reaction is the same as the crystallization reaction of the Nth generation synthesis process. The system may include a carrier or not contain a carrier.

In the present invention, each and every subsequent reaction process includes a crystallization reaction process. Theoretically, it can be achieved by using any possible crystallization method in the prior art. The preferred crystallization method in the present invention is a microwave-powered hydrothermal synthesis reaction, which includes the steps of heating the system to the crystallization temperature at a heating rate of 1-30° C./min, and performing the crystallization reaction at this temperature. Wherein: the heating rate is preferably 15-30°C/min, most preferably 20-25°C/min; the crystallization temperature is 80-130°C, preferably 85-105°C, most preferably 90-100°C; The melting time is 1 to 600 minutes, preferably 10 to 120 minutes, and most preferably 10 to 35 minutes.

For the reaction sol described in the present invention, those skilled in the art can combine the demands for the target product and make a selection according to the prior art. In the present invention, a mixture containing a silicon source, an aluminum source, an alkali source and water is used as the reaction sol. The ratio varies within the following range according to the ratio of synthetic raw materials for different types of molecular sieve membranes: the molar ratio of silicon source, aluminum source, alkali source and water is (5～30):1:(30～90):(900～ 2200); preferably (5 to 25):1:(30 to 70):(900 to 2200); more preferably (5 to 20):1:(50 to 70):(1000 to 2000).

Further, the silicon source, aluminum source, and alkali source that can be used in the above scheme can follow the guidance of the prior art. The silicon source is selected from at least one of silicic acid, silica gel, silica sol, tetraalkyl silicate, sodium silicate, water glass or white carbon black; preferably silicic acid, silica gel, silica sol or tetraoxane silicate At least one of base esters. The aluminum source is selected from at least one of aluminum hydroxide, sodium aluminate, aluminum alkoxide, aluminum nitrate, aluminum sulfate, kaolin or montmorillonite; preferably, it is selected from aluminum hydroxide, sodium aluminate or aluminum nitrate At least one. The alkali source is selected from alkalis with alkali metals or alkaline earth metals as cations; preferably sodium hydroxide or potassium hydroxide.

Among the technical solutions within the above range of conditions, the most important and most suitable target molecular sieve membrane used in the present invention is FAU molecular sieve membrane or LTA molecular sieve membrane. Among them, LTA molecular sieve membranes are particularly preferred, and NaA molecular sieve membranes are most preferred.

Corresponding to the choice of the target molecular sieve membrane, the reaction sol can be exemplified but not limited to: the reaction sol for preparing the FAU film: 70Na ₂ O:1Al ₂ O ₃ :20SiO ₂ :2000H ₂ O; the reaction sol for preparing the LTA film: 50Na ₂ O: 1Al ₂ O ₃ :5SiO ₂ :1000H ₂ O.

In a specific embodiment, the crystallization reaction further includes an aging step, which is to place the seed layer-supported carrier in the reaction sol and let it stand at 30-90° C. for 0-24 h. The aging temperature is preferably 50-70°C, most preferably 55-65°C; the aging time is preferably 5-20h, most preferably 8-18h.

In the follow-up study, it was further discovered that even after the above-mentioned drying treatment of the complex I, the final product still exhibits a problem with high requirements for the stability of the reaction residual liquid: the composition of the reaction residual liquid will fluctuate during the subsequent production process. Affect the stability of the quality of next-generation products; and the reaction residual liquid should usually not be stored for more than 48 hours, otherwise it will cause a large number of defects in the product, and the carrier (composite I) coated with the seed liquid cannot be stored for a long time even after drying; After the continuous production is interrupted, it is necessary to reconstitute the first generation reaction liquid. When the number of generations increases, the change in the composition of the seed solution is often an important factor affecting the stability of high-generation products. This is very unfavorable to the large-scale and flexible production of the factory. On this basis, we further improve the method of the present invention, and disclose a more preferred embodiment of the present invention: on the basis of the above-mentioned technical solution of the present invention, a step of firing the carrier supporting the seed layer is added. Studies have shown that the roasting process helps to activate the molecular sieve seeds in the seed layer supported on the surface of the carrier, which is conducive to the effect of the seeds; the roasting step increases the interaction between the seeds and the carrier, which is conducive to the preparation of a smooth and dense molecular sieve membrane; and Although the seed layer coated on the surface of the carrier is dried, the sol-state seed layer still contains a large amount of alkali. These alkalis will react with the alumina in the carrier during the calcination process, and the formation on the surface of the carrier is beneficial to participate in the molecular sieve membrane. Growth of aluminate ions. Based on the above reasons, the seed layer can significantly promote the growth of the molecular sieve membrane after firing. It is more helpful to obtain molecular sieve membranes with lower requirements for reaction residual liquid, higher synthesis flexibility, better performance and more stable performance.

More specifically, this embodiment including a roasting step can be described as a sustainable synthesis process including a cyclic step. The method includes an N-generation synthesis process, where N is a positive integer; wherein the N-generation synthesis process includes the following steps:

When N=1, the carrier supporting the seed layer is calcined and placed in the reaction sol, and the first-generation molecular sieve membrane is prepared by the crystallization reaction; the reaction residual liquid (mother liquor) is used as the seed crystal for the second-generation synthesis process liquid;

When N≥2:

①Pre-coating seed liquid: take the reaction residue (mother liquor) after the N-1 generation crystallization reaction as the seed liquid, uniformly coat the carrier, and let the coated carrier stand at room temperature until it is completely dry. Carrier supporting the seed layer (composite I);

② After calcining the carrier (composite I) supporting the seed layer, it is cooled to room temperature to obtain the calcined composite carrier (composite II);

③Then put the calcined composite carrier (ie, composite II) in the reaction sol for crystallization reaction;

③Separate the molecular sieve membrane and the reaction residue (mother liquor), (wash the molecular sieve membrane to neutrality, and dry) to obtain the Nth-generation molecular sieve membrane; the mother liquor is used as the seed liquid for the N+1th-generation synthesis process.

In the specific embodiment, the calcination temperature in the calcination step is 100-700° C., and the calcination time is 0.1-24 h. More specifically, the firing temperature is preferably 300 to 600°C. For FAU molecular sieve membranes or LTA molecular sieve membranes, the most preferred calcination temperature is 500±50°C. The calcination time is 0.1-24h, preferably 2-7h, more preferably 3-6h, most preferably 3±0.5h.

For the purpose of keeping the roasting uniform, the system should be warmed up smoothly and smoothly before the roasting process. Therefore, the specific implementation includes the heating rate of the system from room temperature to the roasting temperature at a heating rate of 0.5-30°C/min. process. More preferably, the heating rate is 5°C/min.

The loading of the material on the surface of the carrier before firing will affect the properties of the final film to a certain extent. In the present invention, the amount of substance loaded on the surface of the carrier can be adjusted by adjusting the number of coatings. Specifically, it should be controlled to 1-100mg/cm ² . When applicable to FAU molecular sieve membranes or LTA molecular sieve membranes, the preferred application load is 3 to 26 mg/cm ² , and most preferably 10 to 19 mg/cm ² . The load is characterized by the difference between the calcined mass of the carrier per unit area and the mass of the blank carrier. If the load is too small or too large, it is not conducive to uniform and stable film formation, and it is easy to produce products containing larger defects.

Consistent with the subgeneration synthesis method described earlier, in the technical scheme of the present invention, the calcined composite body further undergoes aging and crystallization reactions. In the technical solution including the roasting step, it is suitable for the aging process of the preparation of FAU molecular sieve membrane or LTA molecular sieve membrane. The preferred aging temperature is 40-80°C, most preferably 45-70°C; the aging time is preferably 5-20h, The best is 8～18h. After aging, the crystallization reaction is continued in the reaction sol, and the preferred crystallization method is a hydrothermal synthesis reaction powered by microwave. It is suitable for the crystallization process of FAU molecular sieve membrane or LTA molecular sieve membrane, the crystallization temperature is 85～105℃, the best is 90～100℃; the crystallization time is preferably 10～120min, and the best is 10～35min.

In the continuous production process of the present invention, the reaction residual liquid of the previous generation synthesis process is used as the seed liquid. The process is simple, the equipment is simple, the cost is low, the reproducibility is good, and the waste discharge can be reduced. It is an environmentally friendly new green and sustainable preparation technology ; And the molecular sieve membrane prepared by the method of the present invention is smooth and compact, and has excellent separation performance. The subgeneration synthesis test of FAU and LTA molecular sieve membranes proved that the subgeneration synthesis method of the present invention can be continuously carried out in a continuous cycle under the condition of ensuring operation specifications and stable conditions. Within the range of the number of generations 2≤N≤50, the performance of the synthesized molecular sieve membranes can be maintained stably to meet industrial needs. In particular, the preferred technical solution including the roasting step further solves the problem that the quality of the product is affected by the change in the composition of the seed liquid, which ensures the stability of the product under the premise of an increase in the number of generations. The number of successive generation synthesis used in the actual industrial operation can be selected and set to the value of N according to the actual production.

The technical solution of the present invention will be further described below in conjunction with non-limiting embodiments to further support the beneficial technical effects mentioned.

In the following examples, unless otherwise specified, the test of alcohol-water separation refers to the method described in Journal Of Materials Science, 43(2008) 3279-3288. The raw material is a 90% ethanol aqueous solution, and the pervaporation temperature is 65°C. Use a water analyzer to test permeation to measure water content.

The reaction sol of the FAU film refers to Journal Of Materials Science, 43 (2008) 3279-3288. According to the molar ratio, the composition of the raw material is 20SiO ₂ :1Al ₂ O ₃ :70Na ₂ O:2000H ₂ O.

The reaction sol of the LTA film refers to Journal Of Membrane Science, 297 (2007) 10-15. According to the molar ratio, the composition of the raw material is 5SiO ₂ :1Al ₂ O ₃ :50Na ₂ O:1000H ₂ O.

Refer to the following definitions for testing and evaluation of molecular sieve membrane products:

1. Separation factor

It represents the ratio of the relative content of the two substances in the material before and after the molecular sieve membrane separation operation. It is defined as:

In the formula, α _i/j represents the separation coefficient of the molecular sieve membrane for components i (preferably permeating through the membrane) and j components; x _i,p (x _j,p ) represents the mass fraction of component i(j) in the permeate ; X _i,f (x _j,f ) represents the mass fraction of component i(j) in the raw material.

2. Permeation flux

According to the specified temperature and pressure, the mass of the material passing through the unit membrane area per unit time. It is defined as:

Among them, J represents the permeation flux (kgm ^-2 h ^-1 ); W represents the mass of the permeable component (kg); Δt represents the sampling interval (h); A represents the effective area of the membrane surface for separation (m ² ) .

Example 1-1

The preparation of FAU molecular sieve membrane products 1 to 4 includes the following steps

(1) Prepare the synthetic liquid according to the following method;

Preparation of solution A ₁ : 15.11g of NaOH is dissolved in 180g of deionized water, and then 1.82g of sodium metaaluminate is added to dissolve to obtain solution A ₁ ;

Solution B ₁ : Dissolve 15.11g of NaOH in 180g of deionized water, then add 33.3g of silica sol (in which _{the mass percentage of SiO 2} is 40%), and dissolve to obtain solution B ₁ ;

Mix the solution A ₁ and the solution B ₁ thoroughly to obtain a uniform and clear synthetic solution. In the resultant synthetic solution, the substances contained are converted into 70Na ₂ O:Al ₂ O ₃ :20SiO ₂ :2000H ₂ O according to the molar ratio.

(2) Transfer the synthesis solution to 4 synthesis kettles; before microwave synthesis, place all synthesis kettles in an oven at 60°C so that the support body is aged for 8 hours in the presence of the synthesis solution; after aging, all synthesis kettles The synthesis kettle was placed in a microwave oven, and the temperature was raised to 95°C at a constant rate within 4 minutes; then the system temperature was maintained at 95°C, and the synthesis kettle was taken out after 20, 25, 30, and 35 minutes of reaction. Pour out the first-generation seed solution in the synthesis kettle for use.

(3) Completely immerse the tubular porous alumina ceramic support with a length of 10cm and a diameter of 1.2cm in the first-generation seed solution obtained in (2), keep it for 15 minutes, and then take it out and dry it naturally at room temperature to obtain a load Carrier for the seed layer. Next, prepare the synthesis solution according to step (1), place the carrier supporting the seed layer vertically in the polytetrafluoroethylene synthesis kettle, and then transfer the synthesis solution to the synthesis kettle; before microwave synthesis, place the synthesis kettle In an oven at 60°C, the carrier supporting the seed layer was aged for 8 hours in the presence of the synthesis solution; after aging, the synthesis kettle was placed in a microwave oven and the temperature was raised to 95°C at a constant rate within 4 minutes; then the system temperature was maintained at 95°C , React for 20 (product 1), 25 (product 2), 30 (product 3), and 35 (product 4) minutes respectively. The reaction time of the first generation seed liquid corresponds to the reaction time of the carrier supporting the seed layer. After the synthesis, the molecular sieve membrane tube is washed, placed and dried to obtain product 1, product 2, product 3, and product 4. The corresponding reaction residues are marked as S-1, S-2, S-3, S-4.

The supported molecular sieve membrane product I prepared in Example 1-1 was subjected to a pervaporation separation performance test. When the permeation temperature is 65°C, the separation results of the ethanol/water system are shown in Table 1-1. The phase of product 3 was examined by X-ray diffraction, and the result is shown in Figure 1. It can be seen from the result that the molecular sieve membrane has the FAU configuration.

Table 1-1

sample	Response time (minutes)	Separation factor	Throughput (kg/m 2 .hr)
Product 1	20	10	3
Product 2	25	90	2.2
Product 3	30	860	1.8
Product 4	35	930	1.2

It can be seen from Table 1-1 that with the increase of the reaction time of the synthetic solution in the reactor, the separation coefficient of the FAU membrane gradually increases, indicating that the molecular sieve membrane becomes denser with the increase of the reaction time. After 30 minutes of reaction, the molecular sieve Although the separation coefficient of the membrane is further increased, the molecular sieve membrane becomes denser and thicker at the same time, so that the permeability of product 4 drops to 1.2, and the increase in selectivity is not enough to offset the benefits brought by the reduced flux.

Example 1-2

The preparation of FAU molecular sieve membrane products 5-15 includes the following steps:

(1) Prepare the synthetic solution according to the method of Example 1-1;

(2) A tubular porous alumina ceramic support with a length of 10 cm and a diameter of 1.2 cm was completely immersed in the reaction residue (S-3) obtained in Example 1-1, kept for 15 minutes, and then taken out at room temperature Condition it to dry naturally to obtain a carrier supporting the seed layer. Next, prepare the synthesis solution according to step (1), place the carrier supporting the seed layer vertically in the polytetrafluoroethylene synthesis kettle, and then transfer the synthesis solution to the synthesis kettle; before microwave synthesis, place the synthesis kettle In an oven at 60°C, the carrier supporting the seed layer was aged and heated for 8 hours in the presence of the synthesis solution; then the synthesis kettle was placed in a microwave oven and the temperature was raised to 95°C at a constant rate within 4 minutes; then the system temperature was maintained at 95°C, React for 30 minutes. After the synthesis is completed, the molecular sieve membrane tube is washed and placed for drying to obtain product 5. The corresponding reaction residue is marked as S-5.

(3) Using the reaction residual liquid obtained in (2) and the method to prepare product 6 and reaction residual liquid S-6.

(4) The operation of the recycle step (3) is followed by synthesis to prepare the eleventh generation product 15 and the reaction residue S-15.

The supported molecular sieve membrane products 5-15 prepared in Example 1-2 were subjected to the pervaporation separation performance test. When the permeation temperature is 65°C, the separation results of the ethanol/water system are shown in Table 1-2.

Table 1-2

sample	Separation factor	Throughput (kg/m 2 .hr)
Product 5	896	1.7
Product 6	860	1.8
Product 7	813	1.9
Product 8	835	1.8
Product 9	828	1.9
Product 10	853	1.8
Product 11	882	1.7

Product 12	832	1.9
Product 13	930	1.6
Product 14	872	1.8
Product 15	828	1.9

It can be seen from Table 1-2 that the separation coefficients of the 11-generation products continuously prepared with successive seed crystals are all between 813 and 896, and the corresponding water concentration in permeation test is 98.8%-98.9%, and the flux is 1.6 It fluctuates between ~1.9, showing very excellent stability.

Example 1-3

The preparation of LTA type molecular sieve membrane products 16-19 includes the following steps

(1) Prepare the synthetic liquid according to the following method;

Preparation of solution A ₁ : Dissolve 21.33g of NaOH in 180g of deionized water, then add 3.64g of sodium metaaluminate to dissolve to obtain solution A ₁ ;

Solution B ₁ : Dissolve 21.33g of NaOH in 180g of deionized water, then add 16.7g of silica sol (containing _{40% by mass of SiO 2} ), and dissolve to obtain solution B ₁ ;

Mix the solution A ₁ and the solution B ₁ thoroughly to obtain a uniform and clear synthetic solution. In the resultant synthetic solution, the substances contained are converted into 50Na ₂ O:Al ₂ O ₃ :5SiO ₂ :1000H ₂ O according to the molar ratio.

(2) Transfer the synthesis solution to 4 synthesis kettles; before microwave synthesis, place all synthesis kettles in an oven at 45°C so that the support body is aged for 18 hours in the presence of synthesis solution; after aging, all synthesis kettles The synthesis kettle was placed in a microwave oven and heated to 100°C at a constant rate within 4 minutes; then the system temperature was maintained at 100°C, and the synthesis kettle was taken out after 10.5, 11.5, 12.5, and 13.5 minutes of reaction, and the first generation seed liquid in the synthesis kettle was poured Out spare.

(3) Completely immerse the tubular porous alumina ceramic support with a length of 10cm and a diameter of 1.2cm in the first-generation seed solution obtained in (2), keep it for 15 minutes, and then take it out and dry it naturally at room temperature to obtain a load Carrier for the seed layer.

(4) Prepare the synthesis solution according to step (1), place the carrier supporting the seed layer vertically in the polytetrafluoroethylene synthesis kettle containing the synthesis solution; before microwave synthesis, place the synthesis kettle in an oven at 45°C for heating 18 hours; then place the synthesis kettle in a microwave oven and heat it up to 100°C at a constant rate within 4 minutes; then maintain the system temperature at 100°C to react 10.5 (product 16), 11.5 (product 17), 12.5 (product 18), and 13.5, respectively (Product 19) minutes, the reaction time of the primary mother liquor corresponds to the reaction time of the carrier supporting the seed layer. The synthesized molecular sieve membrane tube is washed, placed and dried to obtain product 16, product 17, product 18, and product 19. The corresponding reaction residues are marked as S-16, S-17, S-18, S-19.

The supported molecular sieve membrane products 16-19 prepared in Examples 1-3 were subjected to a pervaporation separation performance test. When the permeation temperature is 65°C, the separation results of the ethanol/water system are shown in Table 1-3. The phases of products 16-19 were examined by X-ray diffraction. The results are shown in Figure 2. It can be seen from the results that the configuration of the molecular sieve membrane is LTA type; the surface and cross-sectional morphologies of samples 16-19 were tested by scanning electron microscopy. , The result is shown in Figure 3.

Table 1-3

sample

Response time (minutes)

Separation factor

Throughput (kg/m 2 .hr)

Product 16	10.5	200	0.97
Product 17	11.5	10000	1.18
Product 18	12.5	10000	1.32
Product 19	13.5	10000	0.93

It can be seen from Table 1-3 that with the increase of the reaction time of the synthesis solution in the reactor, the separation coefficient of the LTA membrane increased rapidly from 200 to 10000, indicating that the molecular sieve membrane has grown into a dense membrane at 11.5 min. It can also be seen from the electron microscope image (Figure 3). After 12.5 minutes of reaction, the molecular sieve film thickness increased from 2.2 microns to 3.5 microns, so the permeability of product 19 decreased to 0.93, which was not conducive to the efficient separation of ethanol and water.

Example 1-4

The preparation of 20-30 LTA molecular sieve membrane products includes the following steps

(1) Prepare the synthetic liquid according to the method of Example 1-3;

(2) A tubular porous alumina ceramic support with a length of 10 cm and a diameter of 1.2 cm was completely immersed in the reaction residue (S-18) obtained in Example 1-3, kept for 15 minutes, and then taken out to air at room temperature. A carrier supporting the seed layer is obtained by drying.

(3) Prepare the synthesis solution according to step (1), place the carrier supporting the seed layer vertically in the polytetrafluoroethylene synthesis kettle containing the synthesis solution; before microwave synthesis, place the synthesis kettle in an oven at 45°C for heating 18 hours; then place the synthesis kettle in a microwave oven and heat up to 100°C at a constant rate within 4 minutes; then maintain the system temperature at 100°C and react for 12.5 minutes. After the synthesis is completed, the molecular sieve membrane tube is washed and left to dry to obtain the product 20. The corresponding reaction residue is marked as S-20.

(4) Using the remaining reaction liquid obtained in (3), recycle steps (2) and (3) to prepare product 21 and reaction residual liquid S-21.

(5) The eleventh generation product 30 and the reaction residual liquid S-30 are prepared by cyclic substitution in the same method as in step (4).

The supported molecular sieve membrane products 20-30 prepared in Examples 1-4 were subjected to a pervaporation separation performance test. When the permeation temperature is 65°C, the separation results of the ethanol/water system are shown in Table 1-4. We used a scanning electron microscope to observe the surface and cross-sectional morphology of the fifth-generation products, and the results are shown in Figure 4. It can be seen from the figure that these samples have similar surfaces and thicknesses.

Table 1-4

sample	Separation factor	Throughput (kg/m 2 .hr)
Product 20	10000	1.22
Product 21	10000	1.31
Product 22	10000	1.25
Product 23	10000	1.33
Product 24	10000	1.27
Product 25	10000	1.29
Product 26	10000	1.27

Product 27	10000	1.35
Product 28	10000	1.3
Product 29	10000	1.26
Product 30	10000	1.23

It can be seen from Table 1-4 that the separation coefficients of the 11-generation products continuously prepared by the successive seeding method are all 10000, the corresponding water concentration on the permeate side is 99.9%, and the flux fluctuates between 1.22 and 1.35. A good separation performance stability.

Comparative example 1-1

The preparation of LTA molecular sieve membrane products X1～X10 includes the following steps

(1) Prepare the synthetic liquid according to the following method;

Preparation of solution A ₁ : 15.0 g of NaOH is dissolved in 100 ml of deionized water, and then 0.54 g of metal aluminum foil is added to dissolve to obtain solution A ₁ ;

Solution B ₁ : Dissolve 25.0 grams of NaOH in 75 ml of deionized water, then add 10 ml of silica sol (containing _{30% by mass of SiO 2} ), and dissolve to obtain solution B ₁ ;

Mix the solution A ₁ and the solution B ₁ thoroughly to obtain a homogeneous and clear synthetic solution I. In the obtained synthetic solution I, the substances contained are converted into 50Na ₂ O:Al ₂ O ₃ :5SiO ₂ :1000H ₂ O according to the molar ratio.

(2) Fix the tubular porous alumina ceramic support with a length of 10cm and a diameter of 1.2cm with a bracket, and place it vertically in a polytetrafluoroethylene synthesis kettle containing synthetic liquid; before microwave synthesis, place the synthesis kettle at 45°C Heat it in an oven for 18 hours; then place the synthesis kettle in a microwave oven and raise the temperature to 100°C at a constant rate within 4 minutes; then maintain the system temperature at 100°C and react for 8 minutes. After the synthesis is completed, the molecular sieve membrane tube is washed and placed to dry.

(3) Repeat the above steps (1) to (2) once to obtain the supported molecular sieve membrane product X-1.

(4) Repeat the above steps (1) to (3) nine times to obtain supported molecular sieve membrane products X-2 to X-10, respectively.

The supported molecular sieve membrane product prepared in Comparative Example 1-1 was subjected to pervaporation separation performance test. When the permeation temperature is 65°C, the separation results of different alcohol/water systems are shown in Table 1-5.

Table 1-5

sample	Separation factor	Throughput (kg/m 2 .hr)
Product X-1	10000	1.25
Product X-2	2000	1.43
Product X-3	1263	1.41
Product X-4	10000	1.23
Product X-5	10000	1.31
Product X-6	736	1.52
Product X-7	10000	1.23
Product X-8	3261	1.35

Product X-9	10000	1.09
Product X-10	2653	1.31

It can be seen from Table 1-5 that the LTA molecular sieve membrane synthesized by the traditional method also has good alcohol/water separation performance, and the separation coefficient and permeability of the products are quite different from each other, and the stability of the products is not as good as through continuous The products of Examples 1-4 were prepared by substituting synthetic methods.

Example 2-1. Preparation of LTA film under different conditions of reaction residual liquid of generation 0

The preparation of LTA molecular sieve membrane includes the following steps

(1) Preparation of synthetic liquid and reaction residual liquid

(1-1) Prepare synthetic liquid I according to the following method:

Preparation of solution A ₁ : 15.0 g of NaOH is dissolved in 100 ml of deionized water, and then 0.54 g of metal aluminum foil is added to dissolve to obtain solution A ₁ ;

Solution B ₁ : Dissolve 25.0 grams of NaOH in 75 ml of deionized water, then add 10 ml of silica sol (containing _{30% by mass of SiO 2} ), and dissolve to obtain solution B ₁ ;

Mix the solution A ₁ and the solution B ₁ thoroughly to obtain a homogeneous and clear synthetic solution I. In the obtained synthetic solution I, the substances contained are converted into 50Na ₂ O:Al ₂ O ₃ :5SiO ₂ :1000H ₂ O according to the molar ratio. The corresponding converted molar concentrations are: Na ₂ O, 2.64 mol/L; Al ₂ O ₃ , 0.053 mol/L; SiO ₂ , 0.263 mol/L.

(1-2) Preparation of reaction residue containing LTA molecular sieve:

Transfer the synthesis solution I into the synthesis kettle; before the microwave synthesis, place the synthesis kettle in an oven at 45°C so that the support is aged for 18 hours in the presence of synthesis solution I; after aging, place the synthesis kettle in a microwave oven In 4 minutes, the temperature was increased to 100°C at a constant rate; then the system temperature was maintained at 100°C, and reacted for 10.5 minutes, 11.5 minutes, 12.5 minutes and 13.5 minutes to obtain reaction residues I, II, III, and IV with different compositions for later use.

(2) Coating the seed layer and firing

The obtained reaction residual liquids I, II, III, and IV were used as the first generation seed liquid (N ₁ seed liquid). After immersing the cylindrical support into the reaction residual liquid I for 30 seconds, take it out and dry to obtain the composite I-1 (loading amount is 10mg/cm ² ); after immersing the cylindrical support into the reaction residual liquid II for 30 seconds, Take out and dry to obtain composite II-1 (loading amount is 10mg/cm ² ); after immersing the cylindrical support into reaction residual liquid III for 30s, take it out and air dry to obtain composite III-1 (loading amount is 10mg/cm 2) /cm ² ); the cylindrical support was respectively immersed in the reaction residual liquid IV for 30 s, and then taken out to dry to obtain a composite IV-1 (loading amount of 10 mg/cm ² ).

Then the composites I-1, II-1, III-1, IV-1 are placed in a muffle furnace, and the temperature is increased to 500° C. at a heating rate of 5° C./min, maintained for 180 minutes, and then naturally cooled to room temperature for later use.

(3) Preparation of LTA molecular sieve membrane

Fix the calcined composites I-1, II-1, III-1, IV-1 with brackets, and place them vertically in a polytetrafluoroethylene synthesis kettle containing synthetic solution I; before microwave synthesis, the synthesis kettle Placed in an oven at 45°C to make the composites I-1, II-1, III-1, and IV-1 aged for 18 hours in the presence of synthesis solution I; then place the synthesis kettle in a microwave oven at a constant speed within 4 minutes Raise the temperature to 100°C; then maintain the system temperature at 100°C and react for 12.5 minutes. After completion, the membrane tube and the liquid are separated to obtain molecular sieve membranes M-1, M-2, M-3, and M-4. The results of the pervaporation test are shown in Table 2-1. The NaA molecular sieve membrane synthesized by this method has excellent alcohol/water separation performance. All samples show similar separation performance, with a selectivity of more than 10,000 and a permeability of 1.3kg. /m ² .hr or more. Through roasting, the preparation process of the initial reaction residual liquid has little effect on the performance of the molecular sieve membrane.

table 2-1

Product number	Separation factor	Throughput (kg/m 2 .hr)
M-1	10000	1.36
M-2	10000	1.41
M-3	10000	1.39
M-4	10000	1.43

Example 2-2. The influence of the composition change of the reaction residue on the preparation of LTA film

The preparation of LTA molecular sieve membrane includes the following steps

(1) Preparation of synthetic liquid and reaction residual liquid

(1-1) Prepare synthetic solution I according to the method of step (1-1) in Example 2-1:

(1-2) Prepare the reaction residue III according to the method of step (1-2) in Example 2-1:

(2) Coating of reaction residue and baking of composite

The obtained reaction residual liquid III was divided into four equal parts, 56 g each, numbered a, b, c, and d respectively, as the first generation seed liquid (N ₁ seed liquid). After the cylindrical support was immersed in a for 30 seconds, it was taken out and dried to obtain the composite a1 (loading amount is 10 mg/cm ² ); 5 g of deionization was added to the reaction residue b to simulate the concentration of the solute in the reaction residue during the synthesis process Then, the cylindrical support was immersed in the diluted reaction residual liquid b for 30 seconds, and then taken out to dry to obtain a composite body b1 (loading amount of 10mg/cm ² ); 0.25ml of silica sol (30% SiO ₂ ) Was added to the reaction residual liquid c to simulate the change of the silicon substance in the reaction residual liquid, and then the cylindrical support was immersed in the reaction residual liquid c for 30 s, and then taken out to dry, to obtain a composite body c1 (loading amount is 10 mg/cm ² ). 1g of NaOH was added to the reaction residual liquid d to simulate the change of sodium hydroxide in the reaction residual liquid, and then the cylindrical support was immersed in the reaction residual liquid d for 30s, and then taken out to dry to obtain the composite body to obtain d1 (loading amount is 10mg/cm ² ).

Then put the composites a1, b1, c1, d1 in a muffle furnace, and heat up to 500°C at a heating rate of 5°C/min, hold for 180 minutes, and then naturally cool to room temperature for later use.

(3) Preparation of LTA molecular sieve membrane

(3-1) Fix the calcined composites a1, b1, c1, d1 with brackets, and place them vertically in the polytetrafluoroethylene synthesis kettle, and then transfer the synthesis solution I into the synthesis kettle; before microwave synthesis Put the synthesis kettle in an oven at 45°C so that the composites a1, b1, c1, and d1 are aged for 18 hours in the presence of synthesis solution I; then put the synthesis kettle in a microwave oven and heat up to 100°C at a constant rate within 4 minutes ; Then maintain the system temperature at 100°C and react for 12.5 minutes. After completion, the membrane tube and the liquid are separated to obtain molecular sieve membranes A1, B1, C1, D1, and reaction residual liquids a-1, b-1, c-1, and d-1.

(3-2) Take 1/4 of the reaction residues b-1, c-1, d-1, and add 5g deionized water, 0.25ml silica sol and 1g NaOH respectively to these reaction residues and a-1 is called N ₂ seed solution. After immersing the cylindrical support in 4 kinds of N ₂ seed solution for 30 seconds, take it out and dry it to obtain composite a2, b2, c2 and d2, respectively. ; Then put the composite a2, b2, c2, d2 in a muffle furnace, and heat up to 500 ℃ at a heating rate of 5 ℃/min, and keep it for 180 min; after natural cooling to room temperature, fix the composite with a bracket and place it vertically In the PTFE synthesis kettle, and transfer the synthesis solution I into the synthesis kettle; before the microwave synthesis, place the synthesis kettle in an oven at 45°C, so that the complexes a2, b2, c2, and d2 exist in the synthesis solution I Aging under the conditions for 18 hours; after that, the synthesis kettle was placed in a microwave oven, and the temperature was raised to 100°C at a constant rate within 4 minutes; then the system temperature was maintained at 100°C, and the reaction was carried out for 12.5 minutes. After completion, the membrane tube and the liquid are separated to obtain the second generation (N=2) molecular sieve membrane products A2, B2, C2, D2 and the reaction residual liquid a-2, b-2, c-2, d-2.

(3-3) Repeat the operation of the above step (3-2) to prepare the N-generation molecular sieve membrane products AN, BN, CN, DN (N represents the number of generations, N _max = 10).

The selectivity and permeability of each generation of molecular sieve membrane prepared above are shown in Table 2-2; X-ray diffraction results of samples A1, A5, A10, B1, B5, B10, C5, C10, D5, and D10 are shown in Figure 5. Shown; A1, A5, A10, B1, B5, B10, C5, C10, D5, D10 sample surface and cross-sectional views are shown in Figure 6.

Table 2-2

It can be seen from Figure 5 that the X-ray diffraction peaks of the samples A1, A5, A10, B1, B5, B10, C5, C10, D5, and D10 are all attributed to the LTA molecular sieve diffraction peak and the alumina carrier diffraction peak, and there is no other For any miscellaneous phase, the diffraction peak intensity of each sample is basically the same, indicating that NaA molecular sieve membranes (LTA configuration) with similar crystallinity can be obtained through this example. The surface and cross-sectional morphology of the molecular sieve membrane are shown in Figure 6. It can be seen from the figure that the surface of all samples is flat and compact, and from the cross-sectional results, it can be seen that the thickness of each sample is basically the same at about 2.2um. . Finally, it can be seen from Table 2-2 that the NaA molecular sieve membrane synthesized by this method has excellent alcohol/water separation performance, all samples show similar separation performance, the selectivity is more than 10,000, and the permeability is 1.400kg/m ² Above .hr. The change in the composition of the reaction residue has almost no effect on the LTA molecular sieve membrane prepared by the roasting-assisted subgeneration method.

Example 2-3. The effect of composite roasting temperature on LTA molecular sieve membrane

(1) Preparation of synthetic liquid and reaction residual liquid

(1-1) Prepare synthetic solution I according to the method of step (1-1) in Example 2-1:

(1-2) Prepare the reaction residue III according to the method of step (1-2) in Example 2-1:

(2) Coating of reaction residue and baking of composite

Put the reaction residual liquid III into a beaker, immerse 5 cylindrical supports in the reaction residual liquid a for 30 seconds, and then take them out and dry them, respectively numbered e1, e2, e3, e4, and e5. Among them, e1 is dried and ready for use directly, and the composites e2, e3, e4, and e5 are placed in a muffle furnace and fired at 100, 300, 500, and 700°C, respectively, for 180 minutes, and then naturally cooled to room temperature for use.

(3) Preparation of LTA molecular sieve

Fix the treated complexes e1, e2, e3, e4, and e5 with brackets, and place them vertically in the polytetrafluoroethylene synthesis kettle, and then transfer the synthesis solution I into the synthesis kettle; before the microwave synthesis, the synthesis The kettle was placed in a 45°C oven, so that the composites e1, e2, e3, e4, and e5 were aged for 18 hours in the presence of synthesis solution I; then the synthesis kettle was placed in a microwave oven and the temperature was raised to 100°C at a constant rate within 4 minutes; Then, the system temperature was maintained at 100° C., and the reaction was carried out for 12.5 minutes. After completion, the membrane tube and the liquid are separated to obtain molecular sieve membranes E1, E2, E3, E4, and E5.

Table 2-3

Sample serial number	Separation factor	Throughput (kg/m 2 .hr)
E1	10000	1.22
E2	10000	1.25
E3	10000	1.31
E4	10000	1.43
E5	10000	1.27

The E1 sample was not calcined after coating the mother liquor. It can be seen from Table 2-3 that the E4 molecular sieve membrane obtained through the crystallization process after the composite calcined at 500°C showed the best separation performance, and the separation coefficient was 10000, the throughput is 1.43kg/m ² .hr. Compared with the subsequent seeding method (E1) which does not use the roasting process, adding a 500°C roasting step after coating the reaction residue can effectively improve the pervaporation performance (throughput) of the molecular sieve membrane.

Example 2-4. The influence of the remaining time of the reaction on the preparation of LTA film by the roasting-assisted method

(1) Preparation of synthetic liquid and reaction residual liquid

(1-1) Prepare synthetic solution I according to the method of step (1-1) in Example 2-1:

(1-2) Prepare the reaction residue III according to the method of step (1-2) in Example 2-1:

(2) Coating of reaction residue and baking of composite

The inventor divided the obtained reaction residual liquid III into 5 parts, and left them for 0 day, 1 day, 3 days, 7 days, and 15 days respectively. The 5 cylindrical supports were respectively immersed in the above 5 parts of reaction residue for 30 seconds, taken out and dried, placed in a muffle furnace, roasted at 500°C, kept for 180 minutes, and then naturally cooled to room temperature for later use.

(3) Synthesis of LTA molecular sieve membrane

Fix the treated complexes f1, f2, f3, f4, and f5 with brackets, and place them vertically in the polytetrafluoroethylene synthesis kettle, and then transfer the synthesis solution I into the synthesis kettle; before the microwave synthesis, the synthesis The kettle was placed in a 45°C oven, so that the composites f1, f2, f3, f4, and f5 were aged for 18 hours in the presence of synthesis solution I; then the synthesis kettle was placed in a microwave oven, and the temperature was raised to 100°C at a constant rate within 4 minutes; Then, the system temperature was maintained at 100° C., and the reaction was carried out for 12.5 minutes. After the completion of the separation of the membrane tube and the liquid, molecular sieve membranes F1, F2, F3, F4, F5 are obtained. The pervaporation results of these samples are shown in Table 2-4.

Table 2-4

Sample serial number	Separation factor	Throughput (kg/m 2 .hr)
F1	10000	1.43
F2	10000	1.41
F3	10000	1.39
F4	10000	1.38
F5	10000	1.45

It can be seen from Table 2-4 that the molecular sieve membrane prepared with the aid of roasting shows the best separation performance, the separation coefficient is 10000, and the permeability is around 1.4kg/m ² .hr, indicating that the present invention can be used after standing. LTA molecular sieve membrane with excellent performance can be prepared from the reaction residual liquid.

Example 2-5. Preparation of FAU film by baking-assisted sub-seed method

(1) Prepare synthetic solution II as follows:

Preparation of solution A ₁ : 15.11g of NaOH is dissolved in 180g of deionized water, and then 1.82g of sodium metaaluminate is added to dissolve to obtain solution A ₁ ;

Solution B ₁ : Dissolve 15.11g of NaOH in 180g of deionized water, then add 33.3g of silica sol (in which _{the mass percentage of SiO 2} is 40%), and dissolve to obtain solution B ₁ ;

Mix the solution A ₁ and the solution B ₁ thoroughly to obtain a homogeneous and clear synthetic solution II. In the obtained synthetic solution II, the substances contained are converted into 70Na ₂ O:Al ₂ O ₃ :20SiO ₂ :2000H ₂ O according to the molar ratio.

(2) Preparation of reaction residual liquid V

Transfer the synthesis solution II into the synthesis kettle; before the microwave synthesis, place the synthesis kettle in a 70°C oven, so that the support body is aged for 18 hours in the presence of synthesis solution II; after aging, place the synthesis kettle in a microwave oven In 4 minutes, the temperature was increased to 95°C at a uniform rate; then the system temperature was maintained at 95°C, and the synthesis kettle was taken out after 30 minutes of reaction, and the remaining reaction liquid V in the synthesis kettle was poured out for use.

(3) Coating the remaining liquid of the reaction and baking the composite

The obtained reaction residual liquid V was used as the first generation seed liquid (N ₁ seed liquid). After the cylindrical support was immersed in the reaction residue V for 30 seconds, it was taken out and air-dried to obtain a composite g1 (the load was 10 mg/cm ² , and the load was obtained by mass change after calcination). Then the composite g1 was placed in a muffle furnace, and the temperature was raised to 500° C. at a heating rate of 5° C./min, kept for 180 minutes, and then naturally cooled to room temperature for later use.

(4) Synthesis of FAU molecular sieve membrane

Fix the calcined composite body g1 with brackets, and place them vertically in the polytetrafluoroethylene synthesis kettle, and then transfer the synthesis solution II into the synthesis kettle; before microwave synthesis, place the synthesis kettle in a 70°C oven, The composite body g1 was aged for 18 hours in the presence of synthesis solution II; then the synthesis kettle was placed in a microwave oven, and the temperature was raised to 95°C at a constant rate within 4 minutes; then the system temperature was maintained at 95°C and reacted for 30 minutes. After the completion of the separation of the membrane tube and the liquid, molecular sieve membrane G1 and reaction residual liquid g-1 are obtained.

(4-1) Call g-1 as the N ₂ seed solution, immerse the cylindrical support in the N2 seed solution for 30 seconds, and then take it out to dry to obtain the composite g2; then place the composite g2 in the muffle In the furnace, heat up to 500°C at a heating rate of 5°C/min and keep it for 180 minutes; after naturally cooling to room temperature, fix the complex with a bracket and place it vertically in the polytetrafluoroethylene synthesis kettle, and transfer the synthesis solution II to the synthesis In the kettle; before the microwave synthesis, place the synthesis kettle in a 70°C oven, so that the compound g2 is aged for 18 hours in the presence of the synthesis solution II; then place the synthesis kettle in a microwave oven, and heat up to a constant rate within 4 minutes 95°C; then maintain the system temperature at 95°C and react for 30 minutes. Separate the membrane tube and the liquid to obtain the second generation (N=2) molecular sieve membrane product G2 and the reaction residual liquid g-2.

(4-2) Repeat the operation of the above step (4-1) to prepare the N-generation molecular sieve membrane product GN (N represents the number of generations, N _max = 10).

The supported molecular sieve membrane prepared in Example 2-5 was subjected to a pervaporation separation performance test. When the permeation temperature was 65°C, the separation results of the ethanol/water system are shown in Table 2-5. The phases of the products G1 to G10 were examined by X-ray diffraction, and the results are shown in Figure 7. From the results, it can be seen that the molecular sieve membrane has the FAU configuration.

Table 2-5

Membrane tube number	Separation factor	Throughput (kg/m 2 .hr)
G1	860	1.92
G2	900	1.91
G3	1011	1.99
G4	835	1.94
G5	852	1.96

G6	921	1.93
G7	900	1.95
G8	893	1.97
G9	950	1.93
G10	1015	1.92

It can be seen from Table 2-5 that the FAU type molecular sieve membrane synthesized by this method has excellent alcohol/water separation performance, the permeability is around 1.9kg/m ² .hr, the selectivity is more than 800, and it shows very good performance. Good repeatability.

Example 2-6. The influence of sol layer loading on the synthesis of FAU film

(1) Prepare synthetic solution II according to the steps of Example 2-5 (1):

(2) Prepare the reaction residue V according to the steps of Example 2-5 (2)

(3) Coating the remaining liquid of the reaction and baking the composite

The obtained reaction residual liquid V was used as a seed crystal liquid. After immersing 5 cylindrical supports into the reaction residue V for 30 seconds, they were taken out and dried to obtain 4 complexes p1 (loading amount is 10mg/cm ² ); among them, 2 of the complexes p1 were immersed in the reaction residue V for 30 seconds , Take out and dry to obtain the composite p2 (loading amount is 19mg/cm ² ); In addition, one of the p2 complexes is continuously immersed in the reaction liquid V for 30s, and then taken out to dry, to obtain the composite p3 (loading amount is 31mg/cm 2) ² ); Take a p1 complex and immerse it in deionized water for 30 seconds, then take it out and dry it to obtain a complex p0 (loading amount is 3 mg/cm ² ). Then the composites p0, p1, p2, and p3 are placed in a muffle furnace, and the temperature is increased to 500° C. at a heating rate of 5° C./min, maintained for 180 minutes, and then naturally cooled to room temperature for later use.

(4) Synthesis of FAU molecular sieve membrane

The calcined composites p0, p1, p2, and p3 were fixed with brackets and placed vertically in a polytetrafluoroethylene synthesis kettle, and then molecular sieve membranes P0, P1, P2 were obtained according to the steps of Example 2-5 (4). P3.

The supported molecular sieve membrane prepared in Example 2-6 was subjected to the pervaporation separation performance test. When the permeation temperature is 65°C, the separation results of the ethanol/water system are shown in Table 2-6.

Table 2-6

Membrane tube number	Separation factor	Throughput (kg/m 2 .hr)
P0	300	2.32
P1	996	1.91
P2	933	1.99
P3	10	2.53

It can be seen from Table 2-6 that the loading capacity of the sol layer has a greater impact on the performance of the FAU molecular sieve membrane synthesized by this method. Among them, the FAU membrane prepared by the composite ^{of 10mg/cm 2} and 19mg/cm ^{2 is used.} It has excellent alcohol/water separation performance, the permeability is around 1.9kg/m ² .hr, the selectivity is over 800, and the load is too high or too low, which is not conducive to the preparation of FAU membranes with excellent alcohol/water separation performance.

Example 2-7. The effect of sol layer loading on the synthesis of LTA film

(1) Preparation of synthetic liquid and reaction residual liquid

(1-1) Prepare synthetic solution I according to the method of step (1-1) in Example 2-1:

(1-2) Prepare the reaction residue III according to the method of step (1-2) in Example 2-1:

(2) Coating the remaining liquid of the reaction and baking the composite

The obtained reaction residual liquid III was used as a seed crystal liquid. After immersing the 4 cylindrical supports in the reaction residue III for 30s, take them out and dry to obtain 4 complexes q1 (loading amount is 10mg/cm ² ); among them, 2 of the complexes q1 are immersed in the reaction residue III for 30s , Take it out to dry, and obtain the complex q2 (loading amount is 19mg/cm ² ); in addition, one of the q2 complexes is continuously immersed in the reaction residual liquid III for 30s, and then taken out to dry, to obtain the complex q3 (loading amount is 31mg/cm 2) ² ); Take a q1 complex and immerse it in deionized water for 30 seconds, then take it out and dry it to obtain a complex q0 (with a load of 3 mg/cm ² ). Then the composites q0, q1, q2, and q3 are placed in a muffle furnace, and the temperature is increased to 500° C. at a heating rate of 5° C./min, maintained for 180 minutes, and then naturally cooled to room temperature for later use.

(3) Synthesis of LTA molecular sieve membrane

Fix the calcined complexes q0, q1, q2, and q3 with brackets, and place them vertically in the polytetrafluoroethylene synthesis kettle, and then transfer the synthesis solution I into the synthesis kettle; before microwave synthesis, place the synthesis kettle In an oven at 45°C, the composites q0, q1, q2, and q3 were aged for 18 hours in the presence of synthesis solution I; then the synthesis kettle was placed in a microwave oven and the temperature was raised to 100°C at a constant rate within 4 minutes; then the system temperature was maintained 100°C, react for 12.5 minutes. After completion, the membrane tube and the liquid are separated to obtain molecular sieve membranes Q0, Q1, Q2, and Q3 respectively.

The supported molecular sieve membranes prepared in Examples 2-7 were subjected to the pervaporation separation performance test. When the permeation temperature is 60°C, the separation results of the ethanol/water system are shown in Table 2-7.

Table 2-7

Sample serial number	Separation factor	Throughput (kg/m 2 .hr)
Q0	210	1.5
Q1	10000	1.43
Q2	10000	1.39
Q3	10000	1.03

It can be seen from Table 2-7 that the loading of the sol layer has a greater impact on the performance of the LTA molecular sieve membrane synthesized by this method, and the LTA membrane prepared by the composite ^{with the load of 10mg/cm 2} and 19mg/cm ^{2 is used.} It has excellent alcohol/water separation performance, the permeability is around 1.4kg/m ² .hr, and the selectivity is over 10,000. Too high a load causes a decrease in the permeability, and a too low load leads to a decrease in the selectivity of LTA membrane separation.

Comparative Example 2-1. The influence of the composition change of the reaction residue on the seeding method

Synthesis of LTA Molecular Sieve by Subsequent Seeding Method

(1) Synthesis of reaction residue

(1-1) Prepare synthetic solution I according to the method of step (1-1) in Example 2-1:

(1-2) Prepare the reaction residue III according to the method of step (1-2) in Example 2-1:

(2) Coating of reaction residue

The obtained reaction residual liquid III was divided into four equal parts, each 56 g, respectively numbered h, i, j, and k, as the first generation seed liquid (N ₁ seed liquid). After the cylindrical support was immersed in h for 30s, it was taken out and dried to obtain the composite h1 (loading amount is 10mg/cm ² ); 5g of deionized water was added to the reaction residue i to simulate the solute concentration in the reaction residue during the synthesis process Then, the cylindrical support was immersed in the diluted reaction residue i for 30s, and then taken out to dry to obtain a composite i1 (loading amount of 10mg/cm ² ); 0.25ml of silica sol (30% SiO ₂ ) Add to the reaction residual liquid j to simulate the change of the silicon substance in the reaction residual liquid, then immerse the cylindrical support into the reaction residual liquid j for 30s, take it out and dry, and obtain the composite j1 (loading amount is 10mg/cm ² ). 1g of NaOH was added to the reaction residual liquid k to simulate the change of sodium hydroxide in the reaction residual liquid, and then the cylindrical support was immersed in the reaction residual liquid k for 30s, taken out to dry, and the composite was obtained to obtain k1 (loading amount is 10mg/cm ² ).

(3) Preparation of LTA molecular sieve membrane

(3-1) Fix the naturally dried composite bodies h1, i1, j1, and k1 with brackets, and place them vertically in the polytetrafluoroethylene synthesis kettle, and then transfer the synthesis solution I into the synthesis kettle; synthesize in the microwave Previously, the synthesis kettle was placed in an oven at 45°C, so that the composites h1, i1, j1, and k1 were aged for 18 hours in the presence of synthesis solution I; then the synthesis kettle was placed in a microwave oven, and the temperature was raised to 100 at a constant rate within 4 minutes. ℃; then maintain the system temperature at 100℃ and react for 12.5 minutes. After completion, the membrane tube and the liquid are separated to obtain molecular sieve membranes H1, I1, J1, K1, and reaction residual liquids h-1, i-1, j-1, and k-1.

(3-2) Take 1/4 of the reaction residues i-1, j-1, and k-1, and add 5g such as ionized water, 0.25ml silica sol and 1g of NaOH respectively to the reaction residues. h-1 is called N2 seed liquid, the cylindrical support is immersed in 4 kinds of N2 seed liquid for 30s, and then taken out to dry, to obtain composite a2, b2, c2, and d2 respectively; The bracket fixes the complex and places it vertically in the polytetrafluoroethylene synthesis kettle, and transfers the synthesis solution I into the synthesis kettle; before the microwave synthesis, the synthesis kettle is placed in an oven at 45°C to make the complex h2, i2, J2 and k2 were aged for 18 hours in the presence of synthesis solution I; then the synthesis kettle was placed in a microwave oven, and the temperature was increased to 100°C at a constant rate within 4 minutes; then the system temperature was maintained at 100°C and reacted for 12.5 minutes. After the completion of the separation of the membrane tube and the liquid, the second generation (N=2) molecular sieve membrane products H2, I2, J2, K2 and the reaction residual liquid h-2, i-2, j-2, and k-2 are obtained.

(3-3) Repeat the operation of the above step (3-2) to prepare the N-generation molecular sieve membrane products HN, IN, JN, KN (N represents the number of generations, N _max = 10).

The selectivity and permeability of each generation molecular sieve membrane prepared above are shown in Table 2-8.

Table 2-8

product

Separate

Throughput

product

Separate

Throughput

product

Separate

Throughput

product

Separate

Throughput

Numbering	coefficient	(kg/m 2 .hr)	Numbering	coefficient	(kg/m 2 .hr)	Numbering	coefficient	(kg/m 2 .hr)	Numbering	coefficient	(kg/m 2 .hr)
H1	10000	1.22	I1	5326	1.11	J1	736	0.90	K1	10000	0.10
H2	10000	1.31	I2	3862	1.05	J2	798	1.21	K2	10000	0.99
H3	10000	1.25	I3	3095	0.94	J3	1239	1.41	K3	10000	0.92
H4	10000	1.33	I4	951	2.46	J4	632	0.95	K4	10000	0.90
H5	10000	1.27	I5	861	1.41	J5	91	2.13	K5	10000	0.92
H6	10000	1.29	I6	2163	1.25	J6	139	2.35	K6	10000	0.98
H7	10000	1.27	I7	98	3.48	J7	twenty three	1.14	K7	10000	0.95
H8	10000	1.35	I8	124	3.43	J8	56	2.43	K8	10000	0.97
H9	10000	1.30	I9	18	5.41	J9	1	leak	K9	10000	0.93
H10	10000	1.26	I10	1	leak	J10	1	leak	K10	10000	0.95

It can be seen from Table 2-8 that although the use of the successive seeding method shows better penetration and selectivity, its average penetration is about 1.230kg/m ² .hr, which is lower than the sol layer proposed by the present invention. The roasting method assisted the preparation of molecular sieve membrane (1.410kg/m ² .hr). In addition, when the composition of the mother liquor changes, the molecular sieve membrane prepared by the subsequent seeding method has unstable performance, indicating that the reaction residual liquid has a greater impact on the subsequent seeding method. For example _{, a change in the content of SiO 2} significantly reduces the selectivity of the molecular sieve membrane; a slight change in the content of sodium hydroxide leads to a decrease in the permeability of the molecular sieve membrane. In the process of preparing the molecular sieve membrane by the long-term generation method, the content of silicon, aluminum, and molecular sieve in the mother liquor may change, and failure may occur after the synthesis generation exceeds 10 generations. The present invention overcomes this problem well. Provide reliable technical support for the preparation of molecular sieve membranes with good repeatability and excellent performance.

Comparative Example 2-2: The effect of the rest of the reaction on the synthesis of LTA molecular sieve membranes by the subsequent seeding method

(1) Preparation of synthetic liquid and reaction residual liquid

(1-1) Prepare synthetic solution I according to the method of step (1-1) in Example 2-1:

(1-2) Prepare the reaction residue III according to the method of step (1-2) in Example 2-1:

(2) Coating of reaction residue

Divide the reaction residue III into 5 parts, and place them for 0 days (reaction residue 0), 1 day (reaction residue 1), 3 days (reaction residue 3), 7 days (reaction residue 7), and 15 days. (Reaction residue 15). The five cylindrical supports were respectively immersed in the above reaction residual liquid for 30 seconds, and then taken out to dry. The resulting composites were numbered r1, r2, r3, r4, and r5, respectively.

(3) Synthesis of LTA molecular sieve membrane

Fix the naturally dried composites r1, r2, r3, r4, and r5 with brackets, and place them vertically in the PTFE synthesis kettle, and then transfer the synthesis solution I into the synthesis kettle; before microwave synthesis, The synthesis kettle was placed in an oven at 45°C, so that the complexes r1, r2, r3, r4, and r5 were aged for 18 hours in the presence of synthesis solution I; then the synthesis kettle was placed in a microwave oven and the temperature was raised to 100°C at a constant rate within 4 minutes ; Then maintain the system temperature at 100°C and react for 12.5 minutes. After the completion of the separation of the membrane tube and the liquid, molecular sieve membranes R1, R2, R3, R4, R5 are obtained. The pervaporation results of these samples are shown in Table 2-9.

Table 2-9

Sample serial number	Separation factor	Throughput (kg/m 2 .hr)
R1	10000	1.220
R2	3200	1.110
R3	210	1.390
R4	9	3.580
R5	1	6.450

It can be seen from Table 2-9 that the use of unplaced reaction residue can obtain ^{a molecular sieve membrane with a separation coefficient of 10000 and a permeability of 1.220g/m 2} .hr, and as the reaction residue is placed for longer time , The separation selectivity of the sample obtained without the calcination process of the composite gradually decreases, indicating that if the production process is interrupted, the reaction residue needs to be re-constituted to resume production. By comparison with Examples 2-4, it is further illustrated that the present invention can use long-standing reaction residue to prepare LTA molecular sieve membranes with excellent performance through the aid of roasting, and can save the preparation process of reaction residue required for re-production.

Claims (13)

1. The subsequent synthesis method of the molecular sieve membrane includes the step of pre-coating seed crystals, and is characterized in that the pre-coating seed crystals is a process in which the reaction residue after the crystallization reaction is used as a seed crystal liquid coating carrier.
2. The method according to claim 1, wherein the method comprises an N-generation synthesis process, where N is a positive integer; wherein the N-generation synthesis process includes the following steps:

   When N=1, the carrier supporting the seed layer is placed in the reaction sol, and the first-generation molecular sieve membrane is prepared through the crystallization reaction; the reaction remaining liquid is used as the seed liquid for the second-generation synthesis process;

   When N≥2:

   ①Pre-coated seed crystals: use the reaction residue after the N-1 generation crystallization reaction as seed crystal liquid, uniformly coat the carrier, and let the coated carrier stand at room temperature until it is completely dry to obtain a supported seed layer a;

   ② Put the carrier supporting the seed layer in the reaction sol for crystallization reaction;

   ③Separate the molecular sieve membrane and the reaction residual liquid to obtain the Nth generation molecular sieve membrane; the reaction residual liquid is used as the seed liquid for the N+1 generation synthesis process.
3. The method according to claim 2, wherein the crystallization reaction is a microwave-powered hydrothermal synthesis reaction, which includes heating the system to the crystallization temperature at a temperature rise rate of 1-30°C/min. The step of crystallization reaction is carried out at this temperature.
4. The method according to claim 3, wherein the crystallization temperature is 80-130°C.
5. The method according to claim 2, wherein the reaction sol contains a silicon source, an aluminum source, an alkali source and water, and the molar ratio of the silicon source, aluminum source, alkali source and water is (5-30 ):1:(30～90):(900～2200).
6. The method according to claim 1, wherein the molecular sieve membrane is FAU molecular sieve membrane or LTA molecular sieve membrane.
7. The method according to claim 2, characterized in that, before the crystallization reaction, it further comprises an aging step, which is to place the carrier supporting the seed layer in the reaction sol and let it stand at 30-90°C for 0-24 hours .
8. The method according to claim 2, wherein when N=1, the carrier supporting the seed layer is obtained by uniformly coating the carrier with the seed liquid and standing at room temperature until completely dry, and the first The seed liquid in the substitutive synthesis process is obtained from the reaction sol through crystallization reaction.
9. The method according to claim 1, wherein said 2≤N≤50.
10. The method for the subsequent synthesis of molecular sieve membranes according to claim 1, characterized in that it further comprises a step of firing the seed layer-carrying carrier.
11. The method according to claim 10, wherein the calcination temperature is 100-700°C, and the calcination time is 0.1-24h.
12. The method according to claim 10, wherein the roasting step comprises a heating process of heating the system to the roasting temperature at a heating rate of 0.5-30° C./min.
13. The method according to claim 10, wherein the loading amount of the carrier supporting the seed layer is 1-100 mg/cm ² .

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