阅读说明：本技术 一种超薄ssz-13分子筛膜的绿色合成方法 (Green synthesis method of ultrathin SSZ-13 molecular sieve membrane ) 是由 张延风 邱恒娥 张野 徐宁 孔琳 王明全 于 2019-08-22 设计创作，主要内容包括：本发明涉及一种超薄SSZ-13分子筛膜的绿色合成方法：1)制备全硅CHA分子筛晶种,球磨后得到纳米级全硅CHA晶种；2)将纳米级全硅CHA晶种均匀涂覆到多孔载体管上；3)配制SSZ-13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)所得母液置于同一晶化釜中；5)将晶化釜置于烘箱中水热合成6～12天,合成温度为60～120℃；合成结束后,得到的膜管经洗涤、干燥处理；6)高温焙烧脱除模板剂,得到活化的SSZ-13分子筛膜。本发明在低温下合成超薄SSZ-13分子筛膜,极大的降低了合成温度,在常压下合成SSZ-13分子筛膜,避免了高压晶化釜的使用,同时降低了SSZ-13分子筛膜的厚度至400～700纳米,从而大幅降低了传质阻力,提高了渗透率。此法也可适用于其它分子筛膜的合成。(The invention relates to a green synthesis method of an ultrathin SSZ-13 molecular sieve membrane, which comprises the following steps: 1) preparing all-silicon CHA molecular sieve crystal seeds, and performing ball milling to obtain nano-scale all-silicon CHA crystal seeds; 2) uniformly coating nano-scale all-silicon CHA seed crystals on a porous carrier tube; 3) preparing SSZ-13 molecular sieve membrane synthesis mother liquor; 4) placing the porous carrier tube obtained in the step 2) and the mother liquor obtained in the step 3) into the same crystallization kettle; 5) placing the crystallization kettle in an oven for hydrothermal synthesis for 6-12 days, wherein the synthesis temperature is 60-120 ℃; after the synthesis is finished, washing and drying the obtained membrane tube; 6) and (3) roasting at high temperature to remove the template agent to obtain the activated SSZ-13 molecular sieve membrane. The invention synthesizes the ultrathin SSZ-13 molecular sieve membrane at low temperature, greatly reduces the synthesis temperature, synthesizes the SSZ-13 molecular sieve membrane at normal pressure, avoids the use of a high-pressure crystallization kettle, and simultaneously reduces the thickness of the SSZ-13 molecular sieve membrane to 400-700 nanometers, thereby greatly reducing the mass transfer resistance and improving the permeability. The method is also suitable for the synthesis of other molecular sieve membranes.)

1. A green synthesis method of an ultrathin SSZ-13 molecular sieve membrane is characterized by comprising the following steps:

1) preparing all-silicon CHA molecular sieve crystal seeds, and performing ball milling to obtain nano-scale all-silicon CHA crystal seeds;

2) uniformly coating nano-scale all-silicon CHA seed crystals on a porous carrier tube;

3) preparing SSZ-13 molecular sieve membrane synthesis mother liquor;

4) placing the porous carrier tube obtained in the step 2) and the mother liquor obtained in the step 3) into the same crystallization kettle;

5) placing the crystallization kettle in an oven for hydrothermal synthesis for 4-16 days, wherein the synthesis temperature is 60-120 ℃; after the synthesis is finished, washing and drying the obtained membrane tube;

6) and (3) roasting at high temperature to remove the template agent to obtain the activated SSZ-13 molecular sieve membrane.

2. The green synthesis method of the ultrathin SSZ-13 molecular sieve membrane as claimed in claim 1, wherein the step 1) comprises the following steps: mixing a silicon source, trimethyl ammonium adamantane hydroxide and water, adding hydrofluoric acid after stirring, stirring for 30 minutes to obtain a seed crystal reaction solution, performing hydrothermal crystallization for 2-72 hours at 120-230 ℃ to obtain the all-silicon CHA molecular sieve, and performing ball milling to obtain the nano-scale all-silicon CHA seed crystal.

3. The green synthesis method of the ultrathin SSZ-13 molecular sieve membrane as claimed in claim 2, wherein the molar ratio of the reaction solution for preparing the all-silicon CHA molecular sieve seed crystal in the step 1) is as follows: 1.0SiO₂0.5HF, 0.5 trimethylammonioamantadine hydroxide, 3H₂O。

4. The green synthesis method of the ultrathin SSZ-13 molecular sieve membrane as claimed in claim 1, wherein in step 2), the shape of the porous carrier tube comprises a single-channel tube shape, a multi-channel tube shape, a flat plate shape or a hollow fiber tube shape, the material comprises ceramic, stainless steel, alumina, titanium dioxide, zirconium dioxide, silicon carbide or silicon nitride, and the pore diameter is 2-2000 nm.

5. The green synthesis method of the ultrathin SSZ-13 molecular sieve membrane of claim 1, wherein in the step 2), the coating method of the nano-scale all-silicon CHA seed crystal comprises brushing, dipping, spraying or spin coating; when dip coating is adopted, the concentration of the nano-scale all-silicon CHA crystal seeds is 0.01-1 wt%.

6. The green synthesis method of the ultrathin SSZ-13 molecular sieve membrane as claimed in claim 1, wherein the step 3) comprises the following steps: mixing sodium hydroxide, trimethyl ammonium adamantane hydroxide and water, adding a silicon source, stirring for 2 hours, then adding an aluminum source, and stirring for 2 hours to obtain a SSZ-13 molecular sieve membrane synthesis mother liquor.

7. The green synthesis method of the ultrathin SSZ-13 molecular sieve membrane as claimed in claim 6, wherein the mol ratio of the SSZ-13 molecular sieve membrane synthesis mother liquor is as follows: 0.0 to 0.2Na₂O:1SiO₂:0.0～0.1Al₂O₃:0.1～2.0TMAdaOH:5～200H₂O。

8. The green synthesis method of the ultrathin SSZ-13 molecular sieve membrane of claim 6, wherein the aluminum source comprises aluminum isopropoxide, aluminum hydroxide, elemental aluminum, aluminum salt, aluminum oxide or hydrated aluminum oxide; the silicon source comprises silica sol, silicate ester, silica aerosol or sodium silicate.

9. The green synthesis method of the ultrathin SSZ-13 molecular sieve membrane as claimed in claim 1, wherein the crystallization kettle is placed in a high-temperature oven for hydrothermal synthesis for 6-12 days, and the oven temperature is 80-100 ℃.

10. The green synthesis method of the ultrathin SSZ-13 molecular sieve membrane as claimed in claim 1, wherein in the step 6), the roasting temperature is 370-700 ℃ and the roasting time is 2-8 hours.

Technical Field

The invention relates to a synthesis process of a molecular sieve membrane, in particular to a green synthesis method of an ultrathin SSZ-13 molecular sieve membrane.

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. For example, in CO₂The membrane separation device has the advantages of low energy consumption, continuous operation, low equipment investment, small volume, easy maintenance and the like, so the membrane separation device is very suitable for high CO₂Content of harsh separation environment.

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 in-situ hydrothermal synthesis method usually needs higher synthesis temperature, for example, the synthesis temperature of the SSZ-13 molecular sieve membrane is usually 160-200 ℃, the synthesis pressure is higher, and a high-pressure crystallization kettle is needed. The synthesized molecular sieve membrane is thick, usually about 5 microns, and the corresponding permeability is low, so that the unit price of the membrane tube is too high, and the scale application is not facilitated. There is a strong need in the industry for an inexpensive method for preparing a molecular sieve membrane having high permeability.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provide a green synthesis method of an ultrathin SSZ-13 molecular sieve membrane.

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

a green synthesis method of an ultrathin SSZ-13 molecular sieve membrane is characterized in that the SSZ-13 molecular sieve membrane is synthesized at a low temperature, and the ultrathin SSZ-13 molecular sieve membrane (the thickness is 500 nanometers) is prepared by utilizing the characteristics of being beneficial to nucleation and extremely low in crystal growth rate at the low temperature, so that the mass transfer resistance is greatly reduced, and the permeability is improved. The synthesis temperature is reduced to 100 ℃, the SSZ-13 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, and the method comprises the following steps:

1) preparing all-silicon CHA molecular sieve crystal seeds, and performing ball milling to obtain nano-scale all-silicon CHA crystal seeds;

2) uniformly coating nano-scale all-silicon CHA seed crystals on a porous carrier tube;

3) preparing SSZ-13 molecular sieve membrane synthesis mother liquor;

4) placing the porous carrier tube obtained in the step 2) and the mother liquor obtained in the step 3) into the same crystallization kettle;

5) placing the crystallization kettle in an oven for hydrothermal synthesis for 4-16 days, wherein the synthesis temperature is 60-120 ℃; after the synthesis is finished, washing and drying the obtained membrane tube;

6) and (3) roasting at high temperature to remove the template agent to obtain the activated SSZ-13 molecular sieve membrane.

The step 1) comprises the following steps: mixing a silicon source, trimethyl ammonium adamantane hydroxide and water, stirring for 2 hours, adding hydrofluoric acid, stirring for 30 minutes to obtain a seed crystal reaction solution, performing hydrothermal crystallization for 2-72 hours at 120-230 ℃ to obtain an all-silicon CHA molecular sieve, and performing ball milling to obtain the nano-scale all-silicon CHA seed crystal.

Further, the molar ratio of the reaction liquid for preparing the all-silicon CHA molecular sieve seed crystal is as follows: 1.0SiO₂:0.5HF:0.5TMAdaOH:3H₂O (TMADAOH: trimethylammonioadamantane hydroxide).

Further, in the step 2), the shape of the porous carrier tube comprises a single-channel tubular shape, a multi-channel tubular shape, a flat plate shape or a hollow fiber tubular shape, the material comprises ceramics, stainless steel, aluminum oxide, titanium dioxide, zirconium dioxide, silicon carbide or silicon nitride, and the aperture is 2-2000 nm.

Further, in step 2), the coating method of the nano-scale all-silicon CHA seed crystal comprises brushing, dipping, spraying or spin coating.

Further, when dip coating is adopted, the concentration of the nano-scale all-silicon CHA seed crystal is 0.01-1 wt%.

Step 3) comprises the following steps: mixing sodium hydroxide, trimethyl ammonium adamantane hydroxide (organic template agent, TMADAOH) and water, adding a silicon source, stirring for 2 hours, then adding an aluminum source, and stirring for 2 hours to obtain a SSZ-13 molecular sieve membrane synthesis mother liquor.

Further, the mol ratio of the SSZ-13 molecular sieve membrane synthesis mother liquor is as follows: 0.0 to 0.2Na₂O:1SiO₂:0.0～0.1Al₂O₃:0.1～2.0TMAdaOH:5～200H₂O。

Further, the aluminum source comprises aluminum isopropoxide, aluminum hydroxide, elemental aluminum, aluminum salt, aluminum oxide or hydrated aluminum oxide; the silicon source comprises silica sol, silicate ester, silica aerosol or sodium silicate.

Further, in the step 4), the synthetic mother liquor is placed in an oven to be heated for 10-120 minutes, so that the interior of the crystallization kettle reaches the synthetic temperature.

Further, the crystallization kettle is placed in a high-temperature oven for hydrothermal synthesis for 6-12 days, and the temperature of the oven is 80-120 ℃.

Further, in the step 6), the roasting temperature is 370-700 ℃, and the roasting time is 2-8 hours.

The synthesis of molecular sieve powders is usually carried out at higher temperatures (usually over 100 ℃, the synthesis temperatures of different types of molecular sieves vary greatly), because the reaction rate is fast at high temperatures, which is advantageous for large-scale production. The synthesis of molecular sieves can be achieved at a wide range of temperatures. The traditional synthesis of the molecular sieve membrane is consistent with that of molecular sieve powder, and higher synthesis temperature is adopted. The method prolongs the synthesis time and adopts low-temperature preparation to obtain small molecular sieve crystals and ultrathin films.

Compared with the prior art, the SSZ-13 molecular sieve membrane is synthesized at low temperature, and the ultra-thin SSZ-13 molecular sieve membrane (the thickness is 500 nanometers) is prepared by utilizing the characteristics of being beneficial to nucleation and extremely low in crystal growth rate at low temperature, so that the mass transfer resistance is greatly reduced, and the permeability is improved. The synthesis temperature is reduced to 100 ℃, the SSZ-13 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.

Drawings

FIG. 1 is an SEM (scanning electron microscope) photograph of the surface and cross-section of an SSZ-13 molecular sieve membrane prepared in example 1 of the present invention. Wherein, the picture (a) is an SEM picture of the surface of the membrane; (b) the figure is an SEM photograph of a cross section of the membrane.

FIG. 2 is an SEM photograph of the surface and cross-section of an SSZ-13 molecular sieve membrane prepared in example 2 of the present invention. Wherein, the picture (a) is an SEM picture of the surface of the membrane; (b) the figure is an SEM photograph of a cross section of the membrane.

FIG. 3 is an SEM photograph of the surface and cross-section of an SSZ-13 molecular sieve membrane prepared in example 3 of the present invention. Wherein, the picture (a) is an SEM picture of the surface of the membrane; (b) the figure is an SEM photograph of a cross section of the membrane.

FIG. 4 is an SEM photograph of the surface and cross-section of an SSZ-13 molecular sieve membrane prepared in example 4 of the present invention. Wherein, the picture (a) is an SEM picture of the surface of the membrane; (b) the figure is an SEM photograph of a cross section of the membrane.

FIG. 5 is an SEM photograph of the surface and cross-section of an SSZ-13 molecular sieve membrane prepared in example 5 of the present invention. Wherein, the picture (a) is an SEM picture of the surface of the membrane; (b) the figure is an SEM photograph of a cross section of the membrane.

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.

A green synthesis method of an ultrathin SSZ-13 molecular sieve membrane is characterized in that the SSZ-13 molecular sieve membrane is synthesized at a low temperature, and the ultrathin SSZ-13 molecular sieve membrane (the thickness is 500 nanometers) is prepared by utilizing the characteristics of being beneficial to nucleation and extremely low in crystal growth rate at the low temperature, so that the mass transfer resistance is greatly reduced, and the permeability is improved. The synthesis temperature is reduced to 100 ℃, the SSZ-13 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, and the method comprises the following steps:

1) mixing a silicon source, trimethyl ammonium adamantane hydroxide and water, stirring for 2 hours, and adding hydrofluoric acid, wherein the molar ratio of a reaction solution is as follows: 1.0SiO₂:0.5HF:0.5TMAdaOH:3H₂O (TMADAOH: trimethyl ammonium adamantane hydroxide) is stirred for 30 minutes to obtain a seed crystal reaction solution, hydrothermal crystallization is carried out for 2-72 hours at the temperature of 120-230 ℃ to obtain the all-silicon CHA molecular sieve, and the nano-scale all-silicon CHA seed crystal is obtained after ball milling;

2) uniformly coating nano-scale all-silicon CHA crystal seeds on a porous carrier tube, wherein the adopted shape of the porous carrier tube comprises a single-channel tubular shape, a multi-channel tubular shape, a flat plate shape or a hollow fiber tubular shape, the material comprises ceramic, stainless steel, aluminum oxide, titanium dioxide, zirconium dioxide, silicon carbide or silicon nitride, the aperture is 2-2000 nm, the CHA molecular sieve crystal seeds can be coated on the porous carrier by brushing, dip-coating, spray-coating or spin-coating, and the concentration of the solution of the dip-coated CHA molecular sieve crystal seeds is preferably 0.01-1 wt%;

3) sodium hydroxide, trimethyl ammonium adamantane hydroxide (organic template agent, TMADAOH) and water are mixed according to a molar ratio of 0.0-0.2 Na₂O:1SiO₂:0.0～0.1Al₂O₃:0.1～2.0TMAdaOH:5～200H₂Mixing O, adding silica sol, silicate ester, silica aerosol or sodium silicate and the like serving as silicon sources, stirring for 2 hours, adding aluminum isopropoxide, aluminum hydroxide, simple substance aluminum, aluminum salt, aluminum oxide or hydrated aluminum oxide and the like serving as aluminum sources, and stirring for 2 hours to obtain SSZ-13 molecular sieve membrane synthesis mother liquor;

4) placing the porous carrier tube obtained in the step 2) and the mother liquor obtained in the step 3) into the same crystallization kettle, and heating the synthesized mother liquor in an oven for 10-120 minutes to enable the interior of the crystallization kettle to reach a synthesis temperature;

5) placing the crystallization kettle in an oven for hydrothermal synthesis for 4-16 days, wherein the synthesis temperature is 60-120 ℃; after the synthesis is finished, washing and drying the obtained membrane tube;

6) controlling the roasting temperature to be 370-700 ℃, and roasting at a high temperature for 2-8 hours to remove the template agent, thereby obtaining the activated SSZ-13 molecular sieve membrane.

The following are more detailed embodiments, and the technical solutions and the technical effects obtained by the present invention will be further described by the following embodiments.