阅读说明：本技术 一种全硅高硅分子筛膜及其快速制备方法 (All-silicon high-silicon molecular sieve membrane and rapid preparation method thereof ) 是由 张延风 邱恒娥 徐宁 张野 于 2019-10-31 设计创作，主要内容包括：本发明涉及一种全硅/高硅分子筛膜及其制备方法,该方法包括：(1)制备纳米级分子筛晶种；(2)将纳米级分子筛晶种涂覆到多孔载体管上；(3)配制分子筛膜合成母液；(4)将步骤(2)得到的多孔载体管和步骤(3)所得母液进行晶化；(5)将晶化结束后,将得到的膜管进行洗涤、干燥处理；(6)焙烧脱除模板剂,冷却后得到活化的全硅/高硅分子筛膜。与现有技术相比,本发明具有条件温和、速度快、降低设备投资、可适用于多种分子筛结构等优点。(The invention relates to an all-silicon/high-silicon molecular sieve membrane and a preparation method thereof, wherein the method comprises the following steps: (1) preparing nano-scale molecular sieve crystal seeds; (2) coating nano-scale molecular sieve seeds on a porous carrier tube; (3) preparing a molecular sieve membrane synthesis mother solution; (4) crystallizing the porous carrier tube obtained in the step (2) and the mother liquor obtained in the step (3); (5) after crystallization is finished, washing and drying the obtained membrane tube; (6) roasting to remove the template agent, and cooling to obtain the activated all-silicon/high-silicon molecular sieve membrane. Compared with the prior art, the method has the advantages of mild condition, high speed, reduced equipment investment, suitability for various molecular sieve structures and the like.)

1. A rapid preparation method of an all-silicon/high-silicon molecular sieve membrane is characterized by comprising the following steps:

(1) mixing a template agent, an alkali source and deionized water, adding a silicon source and crystal nuclei, stirring and hydrolyzing to obtain a seed crystal synthetic solution, carrying out hydrothermal crystallization to obtain molecular sieve seed crystals, and carrying out ball milling to obtain nano-scale molecular sieve seed crystals;

(2) coating nano-scale molecular sieve seeds on a porous carrier tube;

(3) mixing a template agent, an alkali source and deionized water, adding ammonium hexafluorosilicate, and stirring to obtain a molecular sieve membrane synthesis mother solution;

(4) crystallizing the porous carrier tube obtained in the step (2) and the mother liquor obtained in the step (3);

(5) after crystallization is finished, washing and drying the obtained membrane tube;

(6) roasting to remove the template agent, and cooling to obtain the activated all-silicon/high-silicon molecular sieve membrane.

2. The method of claim 1, wherein the template in step (1) comprises amantadine or tetrapropylammonium hydroxide, the alkali source comprises ethylenediamine, the silicon source comprises ethyl orthosilicate, and the nuclei comprise DDR molecular sieve nuclei; the temperature of the hydrothermal crystallization is 60-160 ℃, and the time is 1-5 days; the stirring time is 1-5 h.

3. The method for rapidly preparing the all-silicon/high-silicon molecular sieve membrane according to claim 1, wherein the seed crystal synthesis solution obtained in the seed crystal synthesis solution in the step (1) comprises an all-silicon MFI molecular sieve seed crystal synthesis solution or an all-silicon DDR molecular sieve seed crystal synthesis solution; SiO in the all-silicon MFI molecular sieve crystal seed synthetic liquid₂Tetrapropylammonium hydroxide, H₂The molar ratio of O to ethanol is (20-30): 5-10): 300-400): 100; SiO in the all-silicon DDR molecular sieve crystal seed synthetic liquid₂Ethylenediamine, amantadine and H₂The molar ratio of O is (0.1-10): (1-5): 0.1-1):100, and the addition amount of DDR molecular sieve crystal nucleus is 0.5-2% of the mass of the crystal seed synthetic fluid.

4. The method of claim 1, wherein the porous carrier tube in step (2) has a shape of one or more of a single-channel tube, a multi-channel tube, a flat plate or a hollow fiber tube, and is made of one or more of ceramic, stainless steel, alumina, titania, zirconia, silica, silicon carbide or silicon nitride, and has a pore diameter of 2-2000 nm; the coating method includes brushing, dipping, spraying or spin coating.

5. The method of claim 4, wherein the nano-sized seed crystals are dispersed in water to form a nano-sized seed crystal dispersion with a concentration of 0.01-1 ω t%, and then the dipping is performed.

6. The method of claim 1, wherein the template in step (3) comprises amantadine or tetrapropylammonium hydroxide, the alkali source comprises ethylenediamine; the stirring time is 1-5 h; the crystallization temperature in the step (4) is 60-120 ℃, and the crystallization time is 2 hours-8 days.

7. The method for rapidly preparing the all-silicon/high-silicon molecular sieve membrane according to claim 1, wherein the molecular sieve membrane synthesis mother liquor obtained in the step (3) comprises an all-silicon MFI molecular sieve membrane synthesis mother liquor or an all-silicon DDR molecular sieve membrane synthesis mother liquor; SiO in the total-silicon MFI molecular sieve membrane synthesis mother liquor₂Ethylenediamine, tetrapropylammonium hydroxide and H₂The molar ratio of O is 1 (0-4) to (0.05-4) to (20-600); SiO in the all-silicon DDR molecular sieve membrane synthesis mother solution₂Ethylenediamine, amantadine and H₂The molar ratio of O is 1 (0.1-8) to (0.03-1) to (30-300).

8. The method as claimed in claim 1, wherein the calcination time in step (6) is 2-8h, the temperature is 150-700 ℃, the atmosphere is air or ozone, and the temperature increase and decrease rate is 1K/min.

9. An all-silicon/high-silicon molecular sieve membrane prepared by the method of any one of claims 1 to 8, wherein the molecular sieve membrane comprises an all-silicon MFI molecular sieve membrane, a high-silicon MFI molecular sieve membrane, an all-silicon DDR molecular sieve membrane, a high-silicon DDR molecular sieve membrane, an all-silicon CHA molecular sieve membrane, a high-silicon CHA molecular sieve membrane, an all-silicon LTA molecular sieve membrane, a high-silicon LTA molecular sieve membrane, an all-silicon mordenite molecular sieve, a high-silicon mordenite molecular sieve, an all-silicon Beta zeolite molecular sieve membrane or a high-silicon Beta zeolite molecular sieve membrane.

10. The all-silicon/high-silicon molecular sieve membrane of claim 9, wherein the thickness of the molecular sieve membrane is 0.3-3.5 μm.

Technical Field

The invention relates to the field of synthesis of molecular sieve membranes, in particular to an all-silicon/high-silicon molecular sieve membrane and a rapid preparation method thereof.

Background

The inorganic molecular sieve membrane is obtained by preparing a layer of continuous, compact and uniform molecular sieve on a porous carrier. The inorganic molecular sieve membrane has the advantages of uniform pore diameter, high temperature resistance, chemical solvent resistance, capability of ion exchange and the like, so the inorganic molecular sieve membrane has great application potential in the fields of membrane catalytic reaction, gas separation, liquid pervaporation separation, environmental protection and the like. Such as ZSM-5 and Silicalite-1 molecular sieve membranes with MFI structures, the diameter of the pore channel of the molecular sieve membranes is about 0.55 nanometer, and the molecular sieve membranes are suitable for separating normal alkane and isoparaffin, separating alcohol and water, separating xylene isomers and the like.

At present, the methods for preparing inorganic molecular sieve membranes on porous carriers mainly comprise: in-situ hydrothermal synthesis, secondary synthesis, xerogel method, etc. The in-situ hydrothermal synthesis method is to directly put a porous carrier into a synthesis mother solution and grow a molecular sieve into a film on the surface of the carrier under the hydrothermal condition. The method is simple to operate, but the quality of the membrane is influenced by various factors, and the molecular sieve membrane is required to be synthesized by repeated crystallization, so that the molecular sieve membrane is thicker. The secondary synthesis method is to pre-coat seed crystals on the porous carrier, and then place the porous carrier in the synthesis mother solution for in-situ hydrothermal crystallization to form the membrane. The method is an improvement on the in-situ hydrothermal synthesis method.

Chinese patent application No. 200580008446.8 discloses a highly selective supported SAPO membrane prepared by contacting at least one surface of a porous membrane support with an aged synthesis gel. The Chinese patent application with the application number of 200810050714.8 discloses a preparation method of an SAPO-34 molecular sieve membrane for selectively separating methane gas, which synthesizes the SAPO-34 molecular sieve membrane for separating methane gas by adopting a crystal seed induced secondary synthesis method. The traditional hydrothermal synthesis method for preparing the molecular sieve membrane has the advantages of simple method and the like, but the prepared membrane has the thickness of 2-10 microns generally, so that the prepared membrane has larger mass transfer resistance and lower permeability, and is not beneficial to the commercial application of the molecular sieve membrane. Therefore, there is a need to develop a simple and inexpensive method for rapidly preparing an ultra-thin molecular sieve membrane.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provide an all-silicon/high-silicon molecular sieve membrane which has mild condition and high speed, reduces equipment investment and is suitable for various molecular sieve structures and a rapid preparation method thereof.

The purpose of the invention can be realized by the following technical scheme:

a rapid preparation method of an all-silicon/high-silicon molecular sieve membrane comprises the following steps:

(1) mixing a template agent, an alkali source and deionized water, adding a silicon source and crystal nuclei, stirring and hydrolyzing to obtain a seed crystal synthetic solution, carrying out hydrothermal crystallization to obtain molecular sieve seed crystals, and carrying out ball milling to obtain nano-scale molecular sieve seed crystals;

(2) coating nano-scale molecular sieve seeds on a porous carrier tube;

(3) mixing a template agent, an alkali source and deionized water, adding ammonium hexafluorosilicate, and stirring to obtain a molecular sieve membrane synthesis mother solution;

(4) crystallizing the porous carrier tube obtained in the step (2) and the mother liquor obtained in the step (3);

(5) after crystallization is finished, washing and drying the obtained membrane tube;

(6) roasting to remove the template agent, and cooling to obtain the activated all-silicon/high-silicon molecular sieve membrane.

Further, the template in step (1) comprises amantadine or tetrapropylammonium hydroxide, the alkali source comprises ethylenediamine, the silicon source comprises ethyl orthosilicate, and the crystal nucleus comprises DDR molecular sieve crystal nucleus; the temperature of the hydrothermal crystallization is 60-160 ℃, and the time is 1-5 days; the stirring time is 1-5 h.

Further, the seed crystal synthetic fluid obtained in the seed crystal synthetic fluid in the step (1) comprises an all-silicon MFI molecular sieve seed crystal synthetic fluid or an all-silicon DDR molecular sieve seed crystal synthetic fluid; SiO in the all-silicon MFI molecular sieve crystal seed synthetic liquid₂Tetrapropylammonium hydroxide, H₂The molar ratio of O to ethanol is (20-30): 5-10): 300-400): 100; SiO in the all-silicon DDR molecular sieve crystal seed synthetic liquid₂Ethylenediamine, amantadine and H₂The molar ratio of O is (0.1-10): (1-5): 0.1-1):100, and the addition amount of DDR molecular sieve crystal nucleus is 0.5-2% of the mass of the crystal seed synthetic fluid. In the preparation process of the all-silicon DDR molecular sieve crystal seed, a certain amount of DDR molecular sieve is required to be added as a crystal nucleus, which is beneficial to the crystallization process.

Further, the shape of the porous carrier tube in the step (2) comprises one or more of a single-channel tube shape, a multi-channel tube shape, a flat plate shape or a hollow fiber tube shape, the material comprises one or more of ceramics, stainless steel, alumina, titanium dioxide, zirconium dioxide, silicon carbide or silicon nitride, and the pore diameter is 2-2000 nm; the coating method includes brushing, dipping, spraying or spin coating.

Further, in the case of dip coating, the nano-sized seed crystal is dispersed in water to form a nano-sized seed crystal dispersion having a concentration of 0.01 to 1 ω t%, followed by dip coating.

Further, the template in step (3) comprises amantadine or tetrapropylammonium hydroxide, and the alkali source comprises ethylenediamine; the stirring time is 1-5 h; the crystallization temperature in the step (4) is 60-120 ℃, and the crystallization time is 2 hours-8 days.

Further, the molecular sieve membrane synthesis mother liquor obtained in the step (3) comprises an all-silicon MFI molecular sieve membrane synthesis mother liquor or an all-silicon DDR molecular sieve membrane synthesis mother liquor; SiO in the total-silicon MFI molecular sieve membrane synthesis mother liquor₂Ethylenediamine, tetrapropylammonium hydroxide and H₂The molar ratio of O is 1 (0-4) to (0.05-4) to (20-600); SiO in the all-silicon DDR molecular sieve membrane synthesis mother solution₂Ethylenediamine, amantadine and H₂The molar ratio of O is 1 (0.1-8) to (0.03-1) to (30-300).

Further, the roasting time in the step (6) is 2-8h, the temperature is 150-.

The all-silicon/high-silicon molecular sieve membrane prepared by the method is characterized by comprising an all-silicon MFI molecular sieve membrane, a high-silicon MFI molecular sieve membrane, an all-silicon DDR molecular sieve membrane, an all-silicon CHA molecular sieve membrane, a high-silicon CHA molecular sieve membrane, an all-silicon LTA molecular sieve membrane, a high-silicon LTA molecular sieve membrane, an all-silicon mercerized molecular sieve membrane, a high-silicon silk molecular sieve membrane or an all-silicon Beta molecular sieve membrane, a high-silicon Beta molecular sieve membrane and the like.

Furthermore, the thickness of the molecular sieve membrane is 0.3-3.5 μm.

A preparation method of an all-silicon MFI molecular sieve membrane comprises the following steps:

(1) stirring and hydrolyzing the raw material of the seed crystal synthetic liquid to obtain seed crystal synthetic liquid, then carrying out hydrothermal crystallization to obtain molecular sieve seed crystals, and carrying out ball milling to obtain nano-scale molecular sieve seed crystals;

(2) coating nano-scale molecular sieve seeds on a porous carrier tube;

(3) mixing raw materials of the synthetic mother liquor to obtain molecular sieve membrane synthetic mother liquor;

(4) crystallizing the porous carrier tube obtained in the step (2) and the mother liquor obtained in the step (3);

(5) after crystallization is finished, washing and drying the obtained membrane tube;

(6) and (3) removing the template agent by high-temperature vacuum roasting, and cooling to obtain the activated all-silicon MFI molecular sieve membrane.

Further, the preparation method of the molecular sieve seed crystal in the step (1) comprises the following steps: mixing tetrapropylammonium hydroxide and deionized water, then adding tetraethoxysilane, stirring to obtain a seed crystal synthetic solution, and carrying out hydrothermal crystallization to obtain an all-silicon MFI molecular sieve seed crystal (the all-silicon MFI molecular sieve is also called Silicalite-1 molecular sieve); the stirring time is 1-5h, and SiO in the seed crystal synthetic liquid₂Tetrapropylammonium hydroxide, H₂The molar ratio of O and ethanol is (20-30): 5-10): 300-400):100, the temperature of the hydrothermal crystallization is 60-120 ℃, and the time is 24-96 h.

Further, the preparation method of the molecular sieve membrane synthesis mother liquor in the step (3) comprises the following steps: mixing tetrapropylammonium hydroxide and water, adding ethylenediamine, stirring, adding silicon source ammonium hexafluorosilicate, and stirring again to obtain an all-silicon MFI molecular sieve membrane synthesis mother liquor; the stirring time is 30min, the stirring time is 1-5h, and SiO in the MFI molecular sieve membrane synthesis mother liquor₂Ethylenediamine, tetrapropylammonium hydroxide and H₂The molar ratio of O is 1 (0-4) to (0.05-4) to (20-600).

Further, the crystallization time in the step (4) is 1-24h, and the temperature is 60-120 ℃.

Further, the roasting time in the step (6) is 2-8h, the temperature is 370-.

A preparation method of an all-silicon DDR molecular sieve membrane comprises the following steps:

(1) stirring and hydrolyzing the raw material of the seed crystal synthetic liquid to obtain seed crystal synthetic liquid, then carrying out hydrothermal crystallization to obtain molecular sieve seed crystals, and carrying out ball milling to obtain nano-scale molecular sieve seed crystals;

(2) coating nano-scale molecular sieve seeds on a porous carrier tube;

(3) stirring and hydrolyzing the raw materials of the synthetic mother liquor to obtain molecular sieve membrane synthetic mother liquor;

(4) crystallizing the porous carrier tube obtained in the step (2) and the mother liquor obtained in the step (3);

(5) after crystallization is finished, washing and drying the obtained membrane tube;

(6) and (3) removing the template agent by high-temperature vacuum roasting, and cooling to obtain the activated all-silicon DDR molecular sieve membrane.

Further, the preparation method of the molecular sieve seed crystal in the step (1) comprises the following steps: mixing amantadine, deionized water and ethylenediamine, adding tetraethoxysilane after stirring, stirring again to obtain a seed crystal synthetic solution, adding DDR molecular sieve crystal nuclei into the seed crystal synthetic solution, and performing hydrothermal crystallization to obtain DDR molecular sieve seed crystals; the stirring time is 0.5-2h, the stirring time is 1-5h, and SiO in the seed crystal synthetic liquid₂Ethylenediamine, amantadine and H₂The molar ratio of O is (0.1-10): (1-5): 0.1-1):100, the addition amount of DDR molecular sieve crystal nucleus is 0.5-2% of the mass of the crystal seed synthetic liquid, the temperature of the hydrothermal crystallization is 100-.

Further, the preparation method of the molecular sieve membrane synthesis mother liquor in the step (3) comprises the following steps: mixing amantadine and water, adding ethylenediamine, stirring, adding ammonium hexafluorosilicate serving as a silicon source, and stirring again to obtain a full-silicon DDR molecular sieve membrane synthesis mother solution; stirring for 10-60min, and stirring for 1-5h, wherein SiO in the DDR molecular sieve membrane synthesis mother liquor₂Ethylenediamine, amantadine and H₂The molar ratio of O is 1 (0.1-8) to (0.03-1) to (30-300).

Further, the crystallization time in the step (4) is 10 hours to 8 days, and the temperature is 60 ℃ to 120 ℃.

Further, the roasting time in the step (6) is 2-8h, the temperature is 150-.

Compared with the prior art, the invention has the following advantages:

(1) by rapid synthesis of molecular sieve membranes at low temperature: ammonium hexafluorosilicate has extremely high activity, and can synthesize the molecular sieve membrane ultra-fast even at a lower synthesis temperature. For the synthesis of the all-silicon MFI molecular sieve membrane, the synthesis time is only 2-4 h at 100 ℃, and the ultrathin molecular sieve membrane with the thickness as low as 0.3 micron is prepared. The traditional all-silicon MFI molecular sieve membrane is synthesized for 1-2 days at 180 ℃, and the membrane thickness is 1-5 microns. For the synthesis of the all-silicon DDR molecular sieve membrane, only 12-24 hours are needed at 100 ℃, and the membrane thickness is only 1.3 microns. The traditional DDR molecular sieve membrane is usually synthesized for 2-4 days at 160 ℃, and the membrane thickness is 3-5 microns. Therefore, the invention can greatly shorten the synthesis time on the premise of reducing the synthesis temperature, and has extremely high synthesis efficiency. Meanwhile, an ultrathin molecular sieve membrane is obtained, so that the mass transfer resistance is greatly reduced, the permeability is improved, and the method can be suitable for various separation processes such as natural gas purification, air separation, alcohol-water separation, normal alkane-isoparaffin separation, xylene isomer separation and the like;

(2) the synthesis temperature is reduced to 60-100 ℃, the molecular sieve membrane can be synthesized under normal pressure, the use of a high-pressure crystallization kettle is avoided, and the equipment investment is reduced;

(3) the method is a universal method, not only suitable for synthesizing all-silicon and high-silicon MFI molecular sieve membranes and all-silicon DDR molecular sieve membranes, but also suitable for synthesizing all-silicon/high-silicon CHA molecular sieve membranes, all-silicon/high-silicon LTA molecular sieve membranes, all-silicon/high-silicon filament light molecular sieves or Beta molecular sieve membranes and the like.

Drawings

FIG. 1 is an SEM image of an all-silicon MFI molecular sieve membrane prepared in example 1 of the present invention;

FIG. 2 is an SEM image of an all-silicon MFI molecular sieve membrane prepared in example 2 of the present invention;

FIG. 3 is an SEM image of an all-silicon MFI molecular sieve membrane prepared in example 3 of the present invention;

FIG. 4 is an SEM image of an all-silicon MFI molecular sieve membrane prepared in example 4 of the present invention;

FIG. 5 is an SEM image of an all-silicon MFI molecular sieve membrane prepared in example 5 of the present invention;

FIG. 6 is an SEM image of an all-silicon MFI molecular sieve membrane prepared in example 6 of the present invention;

FIG. 7 is an SEM image of an all-silicon DDR molecular sieve membrane prepared in example 7 of the invention;

FIG. 8 is an SEM image of an all-silicon DDR molecular sieve membrane prepared in example 8 of the invention;

FIG. 9 is an SEM image of an all-silicon DDR molecular sieve membrane prepared in example 9 of the invention;

FIG. 10 is an SEM image of an all-silicon DDR molecular sieve membrane prepared in example 10 of the invention;

FIG. 11 is an SEM image of an all-silicon DDR molecular sieve membrane prepared in example 11 of the invention;

FIG. 12 is an SEM image of an all-silicon DDR molecular sieve membrane prepared in example 12 of the invention.

Detailed Description

The present invention will be described in detail with reference to specific examples. The following examples will assist those skilled in the art in further understanding the invention, but are not intended to limit the invention in any way. It should be noted that variations and modifications can be made by persons skilled in the art without departing from the spirit of the invention. All falling within the scope of the present invention.

Example 1

In this example, an all-silicon MFI molecular sieve membrane was synthesized under mild conditions (2 hours at 100 ℃), and the specific steps were as follows:

step 1, mixing tetrapropylammonium hydroxide with deionized water, then adding Tetraethoxysilane (TEOS), stirring for 4 hours to obtain a seed crystal synthetic liquid, wherein the molar ratio of the reaction liquid is as follows: 25SiO₂9TPAOH (tetrapropylammonium hydroxide): 360H₂100EtOH, performing hydrothermal crystallization for 24 hours at 120 ℃ to obtain an all-silicon MFI molecular sieve seed crystal (the all-silicon MFI molecular sieve can also be called Silicalite-1 molecular sieve),obtaining nano-scale all-silicon MFI molecular sieve crystal seeds after ball milling;

and 2, selecting a porous ceramic tube with the aperture of 100nm as a carrier, glazing two ends of the carrier, cleaning, drying, sealing the outer surface by using a tetrafluoro belt, and brushing the nano-scale all-silicon MFI molecular sieve on the inner surface of the ceramic tube.

And 3, mixing tetrapropylammonium hydroxide with water, adding Ethylenediamine (EDA) and stirring for 30 minutes, then adding silicon source ammonium hexafluorosilicate and stirring for 4 hours to obtain the molecular sieve membrane synthesis mother liquor. The preferable molar ratio of the mother liquor is as follows: 1SiO₂:0.576EDA:0.36TPAOH:26.63H₂O。

And 4, placing the porous carrier coated with the nano-scale all-silicon MFI molecular sieve prepared in the step 2 into a crystallization kettle, pouring a synthetic mother solution, heating for 2 hours in a 100 ℃ oven, cooling the reaction kettle, taking out the porous carrier tube, completely cleaning, and drying.

And 5, roasting the all-silicon MFI molecular sieve membrane tube obtained in the step 4 at 400 ℃ for 4 hours, removing the template agent (the heating rate and the cooling rate are both 1K/min), and obtaining a layer of all-silicon MFI molecular sieve membrane on the surface of the membrane tube.

The surface and the section of the obtained all-silicon MFI molecular sieve membrane are shown in figure 1, and the surface of the carrier is completely covered by MFI crystals (typical coffin-shaped crystals) and the cross-linking among the crystals is good (see a picture); the thickness of the film was relatively uniform, about 0.30 microns (see panel b). This is the thinnest all-silicon MFI molecular sieve membrane that can be produced by a simple hydrothermal synthesis method. Moreover, the full-silicon MFI molecular sieve membrane can be prepared only in 2 hours at the low temperature of 100 ℃, which is the fastest synthesis at present, and the synthesis temperature is close to the lowest.

Subjecting the membrane tube containing the obtained all-silicon MFI molecular sieve membrane to CO₂/CH₄Gas separation test, the test conditions were: the temperature was 25 ℃, the atmospheric pressure was 102.4kPa, the feed gas flow was 4000mL/min, and the molar composition was 50/50%. Measuring the gas flow at the permeation side by using a soap film flowmeter; the gas composition on the permeate side was analyzed by gas chromatography (Shimadzu-2014C).

Calculation formula of gas permeability: p is V/(sxp). Wherein V is a permeate gas (CO)₂Or CH₄) The flow rate of (2) is in mol/S, S is the membrane area, m²(ii) a P is the pressure difference between the feed side and the permeate side of the membrane tube, in Pa.

Separation selectivity calculation formula: f ═ pCO₂/pCH₄I.e. CO₂And CH₄The permeability of (c).

CO of the membrane tube₂/CH₄Gas separation test, CO at 0.14MPa₂Has an average value ofCO₂/CH₄The separation selectivity of (3) was an average of 6.

Example 2

This example synthesizes an all-silicon MFI molecular sieve membrane under mild conditions, the only difference from example 1 being a synthesis time of 4 hours (100 degrees celsius).

The surface and the section of the obtained all-silicon MFI molecular sieve membrane are shown in figure 2, and the surface of the carrier is completely covered by MFI crystals (typical coffin-shaped crystals) and the cross-linking among the crystals is perfect (see a picture); the film thickness increased to 0.65 microns with longer synthesis time (see panel b). It is very difficult to prepare the all-silicon MFI molecular sieve membrane with the thickness less than 1 micron by adopting a simple hydrothermal synthesis method.

CO of membrane tube containing obtained all-silicon MFI molecular sieve membrane₂/CH₄Gas separation test results, CO at 0.14MPa₂Has an average value ofCO₂/CH₄The separation selectivity of (a) was 7 on the average.

Example 3

This example synthesizes an all-silicon MFI molecular sieve membrane under mild conditions, the only difference from example 1 being a synthesis time of 6 hours (100 degrees celsius).

The surface and the section of the obtained all-silicon MFI molecular sieve membrane are shown in FIG. 3, and the surface of the carrier is completely covered by MFI crystals (typical coffin-shaped crystals) and the cross-linking among the crystals is perfect (see a picture); the thickness of the film was relatively uniform, about 1.03 microns (see panel b). It is very difficult to prepare the all-silicon MFI molecular sieve membrane with the thickness less than 1 micron by adopting a simple hydrothermal synthesis method.

CO of membrane tube containing obtained all-silicon MFI molecular sieve membrane₂/CH₄Gas separation test results, CO at 0.14MPa₂Has an average value ofCO₂/CH₄The separation selectivity of (a) was 7 on the average.

Example 4

This example synthesizes an all-silicon MFI molecular sieve membrane under mild conditions, the only difference from example 1 being a synthesis time of 12 hours (100 degrees celsius).

The surface and the section of the obtained all-silicon MFI molecular sieve membrane are shown in FIG. 4, and it can be seen from the figure that the surface of the carrier is completely covered by MFI crystals (typical coffin-shaped crystals) and the cross-linking between the crystals is perfect (see a picture); the thickness of the film was relatively uniform, about 2.4 microns (see b).

CO of membrane tube containing obtained all-silicon MFI molecular sieve membrane₂/CH₄Gas separation test results, CO at 0.14MPa₂Has an average value ofCO₂/CH₄The separation selectivity of (a) was an average of 25.

Example 5

This example synthesizes an all-silicon MFI molecular sieve membrane under mild conditions, the only difference from example 1 is that the synthesis time is 24 hours and the synthesis temperature is 75 ℃.

The surface and the section of the obtained all-silicon MFI molecular sieve membrane are shown in FIG. 5, and the surface of the carrier is completely covered by MFI crystals (typical coffin-shaped crystals) and the cross-linking among the crystals is perfect (see a picture); the thickness of the film was relatively uniform, about 2.18 microns (see panel b). It is very difficult to prepare the all-silicon MFI molecular sieve membrane with the thickness less than 1 micron by adopting a simple hydrothermal synthesis method. It can be seen that as the synthesis temperature is decreased from 100 to 75 degrees celsius, the crystallization time is correspondingly extended to 24 hours, but this is still a faster synthesis. The reduction of the synthesis temperature is beneficial to reducing the energy consumption.

CO of membrane tube containing obtained all-silicon MFI molecular sieve membrane₂/CH₄Gas separation test results, CO at 0.14MPa₂Has an average value ofCO₂/CH₄The separation selectivity of (3) was an average of 9.

Example 6

In this example, an all-silicon MFI molecular sieve membrane was synthesized under mild conditions, except that the synthesis time was 72 hours and the synthesis temperature was 75 ℃.

The surface and the section of the obtained all-silicon MFI molecular sieve membrane are shown in FIG. 6, and the surface of the carrier is completely covered by MFI crystals (typical coffin-shaped crystals) and the cross-linking among the crystals is perfect (see a picture); the thickness of the film was relatively uniform, about 1.6 microns (see panel b). As can be seen, the film thickness increased significantly as the synthesis time was increased.

CO of membrane tube containing obtained all-silicon MFI molecular sieve membrane₂/CH₄Gas separation test results, CO at 0.14MPa₂Has an average value ofCO₂/CH₄The separation selectivity of (3) was an average of 9.

In view of the general considerations of examples 1-6, conventional synthesis of all-silicon MFI molecular sieve membranes is typically carried out at 180 ℃ for 1-3 days, with a membrane thickness typically in the range of 2-5 microns (ref 1). The reduction of the synthesis temperature is beneficial to reducing the energy consumption and avoiding the use of an autoclave. Ref 2 low temperature synthesis of MFI molecular sieve membranes was reported but requires 3 days at 100 ℃.

In examples 1-6, the synthesis efficiency was improved by 1 order of magnitude at the same temperature of 100 ℃ for only 2 hours at the fastest. Containing the obtained wholeCO of membrane tube of silicon MFI molecular sieve membrane₂-CH₄The separations have an ultra-high permeability, which is determined by their thin film thickness. To CO₂-CH₄Has certain selectivity which is equivalent to the literature data. Of course, the obtained all-silicon MFI molecular sieve membrane has the pore diameter of 0.55 nm, is most suitable for separating larger hydrocarbon mixtures, such as xylene isomers, normal/iso-butane and the like, and is not suitable for CO₂-CH₄Separation, here only as a system of characterization to demonstrate the separation performance.

Ref 1:J.Gascon,F.Kapteijn,B.Zornoza,V.C.Casado,J.Coronas, Practical approach to zeolitic membranes and coatings:state of the art, opportunities,barriers,and future perspectives,Chem.Mater.24(2012) 2829-2844.

Ref 2:Jonas Hedlund,Fredrik Jareman,Anton-Jan Bons,Marc Anthonis,A masking technique for high quality MFI membranes,Journal of Membrane Science,222(2003)163-179.

Example 7

In the embodiment, the all-silicon DDR molecular sieve membrane is synthesized under mild conditions and is synthesized for 10 hours at 100 ℃. The method comprises the following specific steps:

step 1, mixing amantadine, deionized water and ethylenediamine, stirring for 1 hour, then adding Tetraethoxysilane (TEOS), stirring for 4 hours to obtain seed crystal synthetic solution, 1SiO₂4EDA (ethylenediamine), 0.5ADA (amantadine), 100H₂O, (additionally adding 1% of all-silicon DDR crystal nucleus), synthesizing for 3 days at 160 ℃ to obtain all-silicon DDR molecular sieve crystal seeds, and performing ball milling to obtain nano all-silicon DDR molecular sieve crystal seeds;

and 2, selecting a porous ceramic tube with the aperture of 100nm as a carrier, glazing two ends of the carrier, cleaning, drying, sealing the outer surface with a tetrafluoro belt, and brushing the nano all-silicon DDR molecular sieve seed crystal on the inner surface of the ceramic tube.

Step 3, mixing and stirring amantadine, deionized water and ethylenediamine for 30 minutes, then adding silicon source ammonium hexafluorosilicate, and stirring for 4 hours to obtain the productTo a molecular sieve membrane synthesis mother liquor. The preferable molar ratio of the mother liquor is as follows: 1SiO₂:4EDA:0.5ADA:100H₂O。

And 4, placing the porous carrier coated with the nano all-silicon DDR molecular sieve seed crystal prepared in the step 2 in a crystallization kettle, pouring a synthetic mother solution, heating in a 100 ℃ oven for 10 hours, cooling the reaction kettle, taking out the porous carrier tube, completely cleaning, and drying.

And 5, roasting the full-silicon DDR molecular sieve membrane tube obtained in the step 4 in ozone atmosphere at the temperature of 200 ℃ for 4 hours, and removing the template agent (the heating rate and the cooling rate are both 1K/min) to obtain the full-silicon DDR molecular sieve membrane.

The surface and the section of the obtained all-silicon DDR molecular sieve membrane are shown in FIG. 7, and the surface of the carrier is completely covered by DDR crystals, and the cross-linking among the crystals is good (see a picture); the thickness of the film was relatively uniform, about 0.9 microns (see panel b). This is currently the thinnest all-silicon DDR molecular sieve membrane.

Subjecting the membrane tube containing the obtained all-silicon DDR molecular sieve membrane to CO₂/CH₄Gas separation test, the test conditions were: the temperature was 25 ℃, the atmospheric pressure was 102.4kPa, the feed gas flow was 4000mL/min, and the molar composition was 50/50%. Measuring the gas flow at the permeation side by using a soap film flowmeter; the gas composition on the permeate side was analyzed by gas chromatography (Shimadzu-2014C).

Calculation formula of gas permeability: p is V/(sxp). Wherein V is a permeate gas (CO)₂Or CH₄) The flow rate of (2) is in mol/S, S is the membrane area, m²(ii) a P is the pressure difference between the feed side and the permeate side of the membrane tube, in Pa.

Separation selectivity calculation formula: f ═ pCO₂/pCH₄I.e. CO₂And CH₄The permeability of (c).

CO of membrane tube containing obtained all-silicon DDR molecular sieve membrane₂/CH₄Gas separation test results, CO at 0.14MPa₂Has an average value ofCO₂/CH₄Separation of (2)The average value of selectivity is 145, which is the DDR molecular sieve membrane with highest permeability at present.

Example 8

This example synthesizes an all-silicon DDR molecular sieve membrane under mild conditions.

The difference from example 7 is that: in the step 4, the hydrothermal synthesis time is 24 hours, and the synthesis temperature is still 100 ℃. The rest of the procedure was the same as in example 1.

The surface and the section of the obtained all-silicon DDR molecular sieve membrane are shown in FIG. 8, and as can be seen from the figure, the surface of the carrier is completely covered by DDR crystals, and the cross-linking among the crystals is good (see a picture); the thickness of the film was relatively uniform, about 1.4 microns (see panel b).

CO of membrane tube containing obtained all-silicon DDR molecular sieve membrane₂/CH₄Gas separation test results, CO at 0.14MPa₂Has an average value ofCO₂/CH₄The separation selectivity of (a) was an average of 152. It is clear that the film thickness increases with the increase of the synthesis time, resulting in a decrease in permeability and an increase in selectivity.

Example 9

This example synthesizes an all-silicon DDR molecular sieve membrane under mild conditions.

The difference from example 7 is that: in the step 4, the hydrothermal synthesis time is 72 hours, and the synthesis temperature is still 100 ℃. The remaining procedure was the same as in example 7.

The surface and the section of the obtained all-silicon DDR molecular sieve membrane are shown in FIG. 9, and the surface of the carrier is completely covered by DDR crystals, and the cross-linking among the crystals is good (see a picture); the thickness of the film was relatively uniform, about 1.8 microns (see panel b).

CO of membrane tube containing obtained all-silicon DDR molecular sieve membrane₂/CH₄Gas separation test results, CO at 0.14MPa₂Has an average value ofCO₂/CH₄Has an average value of 182.

Example 10

This example synthesizes an all-silicon DDR molecular sieve membrane under mild conditions.

The difference from example 7 is that: in the step 4, the hydrothermal synthesis time is 96 hours, and the synthesis temperature is still 100 ℃. The remaining procedure was the same as in example 7.

The surface and the section of the obtained all-silicon DDR molecular sieve membrane are shown in FIG. 10, and the surface of the carrier is completely covered by DDR crystals, and the cross-linking among the crystals is good (see a picture); the thickness of the film was relatively uniform, about 2.2 microns (see b).

CO of membrane tube containing obtained all-silicon DDR molecular sieve membrane₂/CH₄Gas separation test results, CO at 0.14MPa₂Has an average value ofCO₂/CH₄The separation selectivity of (a) was 189 average.

Example 11

This example synthesizes an all-silicon DDR molecular sieve membrane under mild conditions.

The difference from example 7 is that: in the step 4, the hydrothermal synthesis time is 144 hours, and the synthesis temperature is still 100 ℃. The remaining procedure was the same as in example 7.

The surface and the section of the obtained all-silicon DDR molecular sieve membrane are shown in FIG. 11, and as can be seen from the figure, the surface of the carrier is completely covered by DDR crystals, and the cross-linking among the crystals is good (see a picture); the thickness of the film was relatively uniform, about 2.7 microns (see b).

CO of membrane tube containing obtained all-silicon DDR molecular sieve membrane₂/CH₄Gas separation test results, CO at 0.14MPa₂Has an average value ofCO₂/CH₄The separation selectivity of (3) was an average value of 223.

Example 12

This example synthesizes an all-silicon DDR molecular sieve membrane under mild conditions.

The difference from example 7 is that: in the step 4, the hydrothermal synthesis time is 192 hours, and the synthesis temperature is still 100 ℃. The remaining procedure was the same as in example 7.

The surface and the section of the obtained all-silicon DDR molecular sieve membrane are shown in FIG. 12, and the surface of the carrier is completely covered by DDR crystals, and the cross-linking among the crystals is good (see a picture); the thickness of the film was relatively uniform, about 3.5 microns (see b).

CO of membrane tube containing obtained all-silicon DDR molecular sieve membrane₂/CH₄Gas separation test results, CO at 0.14MPa₂Has an average value ofCO₂/CH₄The separation selectivity of (a) was an average of 212.

By integrating the embodiments 7 to 12, compared with the all-silicon DDR molecular sieve membrane synthesized by the traditional method, the all-silicon DDR molecular sieve membrane greatly reduces the synthesis temperature from 160 ℃ to 100 ℃, greatly shortens the synthesis time from 2 to 4 days to only 10 hours at least, and simultaneously reduces the membrane thickness from 2 to 5 micrometers to 0.9 micrometer.

Compared with the traditional synthesis, the reduction of the synthesis temperature is beneficial to the reduction of the process energy consumption, and the reduction of the synthesis time improves the synthesis efficiency. And the reduction of the film thickness and the improvement of the permeability reduce the cost of the film tube, thereby being beneficial to the industrial application of the film tube. In addition, the reduction of the synthesis temperature has other benefits, such as avoiding the use of a high-pressure crystallization kettle, reducing the equipment investment and reducing the potential safety hazard.

Example 13

In this example, an all-silicon MFI molecular sieve membrane is synthesized under mild conditions, and the specific steps are as follows:

step 1, mixing tetrapropylammonium hydroxide with deionized water, then adding Tetraethoxysilane (TEOS), stirring for 4 hours to obtain seed crystal synthetic liquid, wherein the molar ratio of the reaction liquidThe mixture ratio is as follows: 20SiO 2₂5TPAOH (tetrapropylammonium hydroxide): 300H₂Performing hydrothermal crystallization on 100EtOH at 60 ℃ for 96 hours to obtain all-silicon MFI molecular sieve crystal seeds, and performing ball milling to obtain nano-scale all-silicon MFI crystal seeds;

and 2, selecting a porous ceramic tube with the aperture of 2-100nm as a carrier, glazing two ends of the carrier, cleaning, drying, sealing the outer surface with a tetrafluoro belt, and brushing the nano-scale all-silicon MFI seed crystal on the inner surface of the ceramic tube.

And 3, mixing tetrapropylammonium hydroxide with water, adding Ethylenediamine (EDA) and stirring for 30 minutes, then adding silicon source ammonium hexafluorosilicate and stirring for 1 hour to obtain the molecular sieve membrane synthesis mother liquor. The preferable molar ratio of the mother liquor is as follows: 1SiO₂:0EDA:0.05TPAOH:20H₂O。

And 4, placing the porous carrier coated with the nano-scale all-silicon MFI seed crystal prepared in the step 2 into a crystallization kettle, pouring a synthetic mother solution, heating in a 60 ℃ oven for 24 hours, cooling the reaction kettle, taking out the porous carrier tube, completely cleaning and drying.

And 5, roasting the all-silicon MFI molecular sieve membrane tube obtained in the step 4 at 370 ℃ for 8 hours in vacuum, and removing the template agent (the heating rate and the cooling rate are both 1K/min) to obtain the all-silicon MFI molecular sieve membrane.

Example 14

In this example, an all-silicon MFI molecular sieve membrane is synthesized under mild conditions, and the specific steps are as follows:

step 1, mixing tetrapropylammonium hydroxide with deionized water, then adding Tetraethoxysilane (TEOS), stirring for 5 hours to obtain a seed crystal synthetic liquid, wherein the molar ratio of the reaction liquid is as follows: 30SiO₂10TPAOH (tetrapropylammonium hydroxide): 400H₂Performing hydrothermal crystallization on 100 ℃ for 24 hours to obtain all-silicon MFI molecular sieve crystal seeds, and performing ball milling to obtain nano-scale all-silicon MFI crystal seeds;

and 2, selecting a porous ceramic tube with the aperture of 100-1000nm as a carrier, sealing the two ends of the carrier with glaze, cleaning, drying, sealing the outer surface with a tetrafluoro belt, and brushing the nano-scale all-silicon MFI seed crystal on the inner surface of the ceramic tube.

Step 3, mixing tetrapropylammonium hydroxide and water, addingAdding Ethylenediamine (EDA) and stirring for 30 minutes, then adding silicon source ammonium hexafluorosilicate and stirring for 5 hours to obtain the molecular sieve membrane synthesis mother liquor. The preferable molar ratio of the mother liquor is as follows: 1SiO₂:4EDA:4TPAOH:600H₂O。

And 4, placing the porous carrier coated with the nano-scale all-silicon MFI seed crystal prepared in the step 2 into a crystallization kettle, pouring the synthetic mother liquor, heating the mother liquor in a 120 ℃ oven for 1 hour, cooling the reaction kettle, taking out the porous carrier tube, completely cleaning and drying the porous carrier tube.

And 5, roasting the all-silicon MFI molecular sieve membrane tube obtained in the step 4 at 700 ℃ for 2 hours in vacuum, and removing the template agent (the heating rate and the cooling rate are both 1K/min) to obtain the all-silicon MFI molecular sieve membrane.

Example 15

In this embodiment, the all-silicon DDR molecular sieve membrane is synthesized under mild conditions, and the specific steps are as follows:

step 1, mixing amantadine, deionized water and ethylenediamine, stirring for 0.5 hour, then adding Tetraethoxysilane (TEOS), stirring for 1 hour to obtain seed crystal synthetic solution, 0.1SiO₂1EDA (ethylenediamine), 0.1ADA (amantadine), 100H₂O, synthesizing at 100 ℃ for 1 day to obtain all-silicon DDR molecular sieve crystal seeds, and performing ball milling to obtain nano all-silicon DDR molecular sieve crystal seeds;

and 2, selecting a porous ceramic tube with the aperture of 2-100nm as a carrier, glazing two ends of the carrier, cleaning, drying, sealing the outer surface with a tetrafluoro belt, and brushing the nano all-silicon DDR molecular sieve seed crystal on the inner surface of the ceramic tube.

And 3, mixing and stirring amantadine, deionized water and ethylenediamine for 10 minutes, then adding silicon source ammonium hexafluorosilicate, and stirring for 1 hour to obtain the molecular sieve membrane synthesis mother liquor. The preferable molar ratio of the mother liquor is as follows: 1SiO₂:0.1EDA:0.03ADA:30H₂O。

And 4, placing the porous carrier coated with the nano all-silicon DDR molecular sieve seed crystal prepared in the step 2 in a crystallization kettle, pouring synthetic mother liquor, heating in a 120 ℃ oven for 10 hours, cooling the reaction kettle, taking out the porous carrier tube, completely cleaning and drying.

And 5, roasting the all-silicon DDR molecular sieve membrane tube obtained in the step 4 for 2 hours at the temperature of 150 ℃ in an ozone atmosphere, and removing the template agent (the heating rate and the cooling rate are both 1K/min), so as to obtain the all-silicon MFI molecular sieve membrane.

Example 16

In this embodiment, the all-silicon DDR molecular sieve membrane is synthesized under mild conditions, and the specific steps are as follows:

step 1, mixing amantadine, deionized water and ethylenediamine, stirring for 2 hours, then adding Tetraethoxysilane (TEOS), stirring for 5 hours to obtain a seed crystal synthetic solution, 10SiO₂5EDA (ethylenediamine), 1ADA (amantadine), 100H₂O, synthesizing at 200 ℃ for 5 days to obtain all-silicon DDR molecular sieve crystal seeds, and performing ball milling to obtain nano all-silicon DDR molecular sieve crystal seeds;

and 2, selecting a porous ceramic tube with the aperture of 100-1000nm as a carrier, sealing glaze at two ends of the carrier, cleaning, drying, sealing the outer surface by using a tetrafluoro belt, and brushing the nano all-silicon DDR molecular sieve seed crystal on the inner surface of the ceramic tube.

And 3, mixing and stirring amantadine, deionized water and ethylenediamine for 60 minutes, then adding silicon source ammonium hexafluorosilicate, and stirring for 5 hours to obtain the molecular sieve membrane synthesis mother liquor. The preferable molar ratio of the mother liquor is as follows: 1SiO₂:8EDA:1ADA:300H₂O。

And 4, placing the porous carrier coated with the nano all-silicon DDR molecular sieve seed crystal prepared in the step 2 in a crystallization kettle, pouring a synthetic mother solution, heating in a 60 ℃ oven for 8 days, cooling the reaction kettle, taking out the porous carrier tube, completely cleaning, and drying.

And 5, roasting the all-silicon DDR molecular sieve membrane tube obtained in the step 4 in ozone atmosphere at 250 ℃ for 8 hours, and removing the template agent (the heating rate and the cooling rate are both 1K/min) to obtain the all-silicon DDR molecular sieve membrane.

In the description herein, references to the description of "one embodiment," "an example," "a specific example" or the like are intended to mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

The embodiments described above are intended to facilitate the understanding and use of the invention by those skilled in the art. It will be readily apparent to those skilled in the art that various modifications to these embodiments may be made, and the generic principles described herein may be applied to other embodiments without the use of the inventive faculty. Therefore, the present invention is not limited to the above embodiments, and those skilled in the art should make improvements and modifications within the scope of the present invention based on the disclosure of the present invention.