阅读说明：本技术 一种基于微波加热合成sapo-34分子筛膜的方法 (Method for synthesizing SAPO-34 molecular sieve membrane based on microwave heating ) 是由 张伏军 王鹏飞 徐华胜 余金鹏 张春秀 胡杰 于 2020-11-25 设计创作，主要内容包括：本发明涉及一种基于微波加热合成SAPO-34分子筛膜的方法,包括以下步骤：1)晶种涂敷液的制备：将铝源、磷酸、模板剂及水混合后形成溶胶,之后在常温下搅拌老化,再加入SAPO-34分子筛颗粒并搅拌；2)晶种层的制备：将载体预处理后置于晶种涂敷液中,先进行真空抽吸,再置于微波反应器中进行微波加热,后经干燥；3)分子筛膜的晶化合成：将含有晶种层的载体置于反应釜中,并向反应釜中加入分子筛膜母液,之后在微波反应器中进行升温晶化,经洗涤、干燥后,脱除模板剂。与现有技术相比,本发明引入了微波加热合成技术,合成时间短,所制备的SAPO-34分子筛膜致密,膜厚度均匀且膜厚度可调控,同时具备良好的渗透性和分离性能。(The invention relates to a method for synthesizing an SAPO-34 molecular sieve membrane based on microwave heating, which comprises the following steps: 1) preparation of seed crystal coating liquid: mixing an aluminum source, phosphoric acid, a template agent and water to form sol, then stirring and aging at normal temperature, adding SAPO-34 molecular sieve particles, and stirring; 2) preparing a seed crystal layer: pretreating a carrier, placing the pretreated carrier into a seed crystal coating liquid, performing vacuum suction, placing the carrier into a microwave reactor for microwave heating, and drying; 3) crystallization synthesis of molecular sieve membrane: and (3) placing the carrier containing the seed crystal layer in a reaction kettle, adding the molecular sieve membrane mother liquor into the reaction kettle, then heating and crystallizing in a microwave reactor, and removing the template agent after washing and drying. Compared with the prior art, the invention introduces the microwave heating synthesis technology, has short synthesis time, and the prepared SAPO-34 molecular sieve has compact membrane, uniform and adjustable membrane thickness, and simultaneously has good permeability and separation performance.)

1. A method for synthesizing an SAPO-34 molecular sieve membrane based on microwave heating is characterized by comprising the following steps:

1) preparation of seed crystal coating liquid: mixing an aluminum source, phosphoric acid, a template agent and water to form sol, then stirring and aging at normal temperature, adding SAPO-34 molecular sieve particles, and stirring to obtain a seed crystal coating liquid;

2) preparing a seed crystal layer: pretreating a carrier, placing the pretreated carrier in seed crystal coating liquid, performing vacuum suction, placing the carrier in a microwave reactor for microwave heating, and drying to obtain a carrier containing a seed crystal layer;

3) crystallization synthesis of molecular sieve membrane: and (3) placing the carrier containing the seed crystal layer in a reaction kettle, adding the molecular sieve membrane mother liquor into the reaction kettle, then heating and crystallizing in a microwave reactor, washing, drying, and removing the template agent to obtain the SAPO-34 molecular sieve membrane.

2. The method for synthesizing the SAPO-34 molecular sieve membrane based on microwave heating as claimed in claim 1, wherein in the step 1), Al is contained in the sol₂O₃、P₂O₅Template and H₂The molar ratio of O is 1 (1-2) to (0.15-4) to (15-50); the stirring and aging time is 10-14 h.

3. The method for synthesizing the SAPO-34 molecular sieve membrane based on microwave heating as claimed in claim 1, wherein in the step 1), the SAPO-34 molecular sieve particles have a particle size of 10-600 nm; in the seed crystal coating liquid, the content of SAPO-34 molecular sieve particles is 0.5-2 wt%.

4. The method for synthesizing the SAPO-34 molecular sieve membrane based on microwave heating as claimed in claim 1, wherein in step 2), the carrier is alpha-Al₂O₃A ceramic tube carrier; the pretreatment process comprises the following steps: calcining the carrier at the temperature of 350-750 ℃ for 1.5-2.5h, cooling, polishing the carrier by using 300-500-mesh sand paper, cleaning, and drying in an oven at the temperature of 150-200 ℃ for 1.5-2.5 h.

5. The method for synthesizing the SAPO-34 molecular sieve membrane based on microwave heating as claimed in claim 1, wherein in the step 2), the pressure is 0.01-0.03MPa and the time is 25-35s during the vacuum pumping process.

6. The method for synthesizing the SAPO-34 molecular sieve membrane based on microwave heating as claimed in claim 1, wherein in the step 2), the temperature is 80-150 ℃ and the time is 0.5-3h during the microwave heating.

7. The method for synthesizing the SAPO-34 molecular sieve membrane based on microwave heating as claimed in claim 1, wherein in step 3), the molecular sieve membrane mother liquor is prepared by the following steps: adding an aluminum source into water, stirring and wetting, then adding phosphoric acid, fully hydrolyzing, then adding a silicon source and a template agent to form sol, stirring and aging at room temperature for 0.5-4 days to obtain the molecular sieve membrane mother liquor; in the sol, Al₂O₃、P₂O₅、SiO₂Template and H₂The molar ratio of O is 1 (1-2): (0.05-0.5): 0.15-4): 15-200.

8. The method for synthesizing the SAPO-34 molecular sieve membrane based on microwave heating according to claim 7, wherein the aluminum source comprises one or more of pseudo-boehmite, aluminum isopropoxide, SB powder, aluminum hydroxide or aluminum oxide; the silicon source comprises one or more of silica sol, tetramethyl orthosilicate, tetraethyl orthosilicate, tetrapropyl orthosilicate or tetrabutyl orthosilicate; the template agent comprises one or more of triethylamine, diethylamine, marlin, tetraethylammonium hydroxide or tetrapropylammonium bromide.

9. The method for synthesizing the SAPO-34 molecular sieve membrane based on microwave heating as claimed in claim 1, wherein in the step 3), the temperature-rising crystallization process comprises: the temperature is raised from room temperature to 220 ℃ for crystallization, the temperature raising rate is 2.5-3.5 ℃/min, and the crystallization time is 8-26 h.

10. The method for synthesizing the SAPO-34 molecular sieve membrane based on microwave heating as claimed in claim 1, wherein in the step 3), the template removal process comprises: heating from room temperature to 110-130 deg.C, maintaining for 1.5-2.5h, heating to 580-620 deg.C, maintaining for 1.5-2.5h, and heating rate of 0.8-1.2 deg.C/min.

Technical Field

The invention belongs to the technical field of molecular sieve membrane preparation, and relates to a method for synthesizing an SAPO-34 molecular sieve membrane based on microwave heating.

Background

At present, molecular sieve membranes are widely applied to the fields of organic solvent dehydration, gas separation and the like. SAPO-34 molecular sieve is widely concerned as a catalyst active component in the reaction of preparing low-carbon olefin by methanol, and the SAPO-34 molecular sieve membrane is used for treating CH because of the unique pore channel structure of the SAPO-34 molecular sieve₄/CO₂The separation of the mixed gas has unique advantages and good industrial application prospect. With the development of the technology, the SAPO-34 molecular sieve membrane can combine the catalytic activity and the separation performance thereof as a catalytic separation integrated membrane to be applied to industrial devices. However, the formation of the molecular sieve membrane is a very complex process, and the growth mechanism of the molecular sieve membrane needs to be studied deeply to control the growth, morphology, membrane performance and the like of the molecular sieve so as to obtain a membrane material with higher application value.

At present, the main synthesis methods of SAPO-34 molecular sieve membranes are in-situ synthesis and secondary synthesis.

The difficulty of synthesizing a continuous, compact and high-efficiency membrane by adopting an in-situ hydrothermal synthesis method is relatively high, and usually, the method can only be used for making up for the membrane by adopting a multi-time synthesis method. However, not only does the synthesis complexity increase, but also the crystals already synthesized are prone to crystal transformation and dissolution. In addition, the thickness of the molecular sieve membrane synthesized by the in-situ synthesis method is not easy to control, and an excessively thick or uneven membrane is generally easily formed. Molecular sieve crystals also do not guarantee preferential growth on the substrate surface, rather than nucleation in the synthetic membrane solution. Due to the above problems, the development of in situ synthesis methods has been greatly limited.

The secondary synthesis is an improvement over the in situ synthesis, which separates the nucleation phase from the growth phase of the zeolite molecular sieve crystal growth. Coating seed crystal on the surface of the support in advance to replace crystal nucleus in the in-situ synthesis process, wherein the seed crystal layer loaded on the support can be used as a growth center under certain crystallization conditions, so that the synthesis time can be shortened, and the thickness of the film layer and the microstructure of zeolite molecular sieve crystals can be better controlled; the influence of the support on the film forming process can be reduced by the modification effect of the crystal on the surface of the support, and the generation of defects is avoided. Chinese patent CN106957062A discloses a preparation method of a high-flux oriented SAPO-34 molecular sieve membrane, which adopts a sheet-shaped nano SAPO-34 molecular sieve as a seed crystal, strictly controls the thickness of a seed crystal layer on a porous carrier, and the oriented molecular sieve membrane is more beneficial to the adsorption and diffusion of molecules in the pore channels of the molecular sieve and can improve the flux of the membrane. In addition, Chinese patent CN104058426A discloses a method for synthesizing SAPO-34 molecular sieve membrane by two-step temperature-changing crystallization. The molecular sieve membrane synthesized by the method has the advantages that due to the limitation of the synthesis time of the molecular sieve, the mother liquor generates an up-down concentration gradient along with the time in the static synthesis process, the molecular sieve generated in the mother liquor is accumulated on the lower half part along with the action of gravity, so that the upper thickness and the lower thickness of the molecular sieve membrane are uneven, cracks and defects are easy to occur in high-temperature roasting activation, the gas separation is greatly influenced, the operation is complex, and the method is not suitable for industrial amplification. If a homogeneous dynamic synthesis molecular sieve membrane is adopted, the molecular sieve attached to the surface of the carrier is easy to fall off due to the impact force generated by the continuous flow of the mother solution.

In addition, the experimental conditions for synthesizing the molecular sieve membrane by the existing method are often similar to the synthesis conditions of the corresponding molecular sieve crystal, but because the substrate properties of different molecular sieve membranes are different, the requirements of the molecular sieve membrane on the substrate physicochemical properties and the synthesis membrane conditions are much more rigorous than those of the molecular sieve crystal synthesized singly, and the difficulty in preparing the high-quality molecular sieve membrane is increased.

Disclosure of Invention

The invention aims to provide a method for synthesizing an SAPO-34 molecular sieve membrane based on microwave heating. The invention introduces a microwave heating synthesis technology, has short synthesis time, and the prepared SAPO-34 molecular sieve has compact membrane, uniform membrane thickness, adjustable membrane thickness and good permeability and separation performance.

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

a method for synthesizing a SAPO-34 molecular sieve membrane based on microwave heating comprises the following steps:

1) preparation of seed crystal coating liquid: mixing an aluminum source, phosphoric acid, a template agent and water to form sol, then stirring and aging at normal temperature, adding SAPO-34 molecular sieve particles, and stirring to obtain a seed crystal coating liquid;

2) preparing a seed crystal layer: pretreating a carrier, placing the pretreated carrier into seed crystal coating liquid, performing vacuum suction, placing the carrier into a microwave reactor for microwave heating, and drying (at 100 ℃) to obtain the carrier containing the seed crystal layer;

3) crystallization synthesis of molecular sieve membrane: and (3) placing the carrier containing the seed crystal layer in a reaction kettle, adding the molecular sieve membrane mother liquor into the reaction kettle, then heating and crystallizing in a microwave reactor, washing, drying, and removing the template agent to obtain the SAPO-34 molecular sieve membrane.

Further, in the step 1), Al is contained in the sol₂O₃、P₂O₅Template and H₂The molar ratio of O is 1 (1-2) to (0.15-4) to (15-50); the stirring and aging time is 10-14 h.

Further, in the step 1), the particle size of the SAPO-34 molecular sieve particles is 10-600 nm; in the seed crystal coating liquid, the content of SAPO-34 molecular sieve particles is 0.5-2 wt%. Conventional SAPO-34 molecular sieves can be pretreated into nanosized SAPO-34 molecular sieve particles by one or more of mechanical crushing, acid etching, alkali etching, or hydrothermal treatment.

Further, in the step 2), the carrier is alpha-Al₂O₃A ceramic tube carrier; the pretreatment process comprises the following steps: calcining the carrier at 350-750 deg.C for 1.5-2.5h, cooling, grinding with 300-500 mesh sand paper, cleaning (preferably ultrasonic cleaning), and placing at 150-200 deg.CIs dried in the oven for 1.5 to 2.5 hours.

Further, in the step 2), in the vacuum suction process, the pressure is 0.01-0.03MPa, and the time is 25-35 s.

Further, in the step 2), the temperature is 80-150 ℃ in the microwave heating process, and the time is 0.5-3 h.

Further, in step 3), the preparation process of the molecular sieve membrane mother liquor comprises: adding an aluminum source into water, stirring and wetting, then adding phosphoric acid, fully hydrolyzing, then adding a silicon source and a template agent to form sol, stirring and aging at room temperature for 0.5-4 days to obtain the molecular sieve membrane mother liquor; in the sol, Al₂O₃、P₂O₅、SiO₂Template and H₂The molar ratio of O is 1 (1-2): (0.05-0.5): 0.15-4): 15-200.

Further, the aluminum source comprises one or more of pseudo-boehmite, aluminum isopropoxide, SB powder, aluminum hydroxide or aluminum oxide; the silicon source comprises one or more of silica sol, tetramethyl orthosilicate, tetraethyl orthosilicate, tetrapropyl orthosilicate or tetrabutyl orthosilicate; the template agent comprises one or more of triethylamine, diethylamine, marlin, tetraethylammonium hydroxide or tetrapropylammonium bromide. The aluminum source and the template agent of the seed crystal coating liquid and the molecular sieve membrane mother liquid are the same.

Further, in the step 3), the temperature-rising crystallization process is as follows: the temperature is raised from room temperature to 220 ℃ for crystallization, the temperature raising rate is 2.5-3.5 ℃/min, and the crystallization time is 8-26 h.

Further, in the step 3), the template agent removing process is as follows: heating from room temperature to 110-130 deg.C, maintaining for 1.5-2.5h, heating to 580-620 deg.C, maintaining for 1.5-2.5h, and heating rate of 0.8-1.2 deg.C/min. And naturally cooling to room temperature after the template agent is removed.

Compared with other types of molecular sieve membranes, the SAPO-34 molecular sieve membrane has obvious differences, higher synthesis temperature requirement, more rigorous synthesis conditions and more complex membrane forming mechanism, and more complex procedures are required to ensure the high quality of the membrane. The method adopts a microwave heating mode, can greatly shorten the synthesis time, lightens the influence caused by concentration gradient, has no temperature gradient in a synthesis system, provides a good environment for the growth of a molecular sieve membrane, and has the advantages of simple and convenient operation, good repeatability and easy industrial amplification.

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

1) according to the invention, a special process is adopted in the preparation of the seed crystal layer, AlPO-34 mother liquor and nano SAPO-34 molecular sieve crystals are mixed to serve as seed crystal coating liquid, the seed crystal layer is prepared by vacuum suction, and then the seed crystal layer is treated in a microwave heating mode, so that the seed crystal layer is bonded with a carrier more tightly, the seed crystal layer has more reaction nucleation centers, and further the SAPO-34 molecular sieve membrane which is good in repeatability, high in quality and easy to industrialize is prepared.

2) The microwave heating technology ensures that the reaction temperature of the whole membrane synthesis system is consistent, greatly shortens the reaction time, and effectively avoids the problem that the membrane separation performance is influenced by the defect of the membrane caused by the concentration difference of the reaction system due to overlong reaction time.

3) The invention combines the secondary synthesis method and the microwave heating technology, the thickness of the SAPO-34 molecular sieve membrane is easy to control, and the SAPO-34 molecular sieve membrane has good continuity, compactness, high crystallinity and simple preparation process.

Drawings

FIG. 1 is an X-ray diffraction (XRD) pattern of a SAPO-34 molecular sieve membrane prepared in example 1;

FIG. 2 is a surface SEM photograph of a ceramic tube support of example 1;

FIG. 3 is a sectional SEM photograph of the ceramic tube support of example 1;

FIG. 4 is an SEM image of SAPO-34 molecular sieve particles obtained after pretreatment of conventional SAPO-34 molecular sieve in example 1;

FIG. 5 is a surface SEM image of a carrier containing a seed layer of example 1;

FIG. 6 is an SEM image of the surface (a) and cross section (b) of a SAPO-34 molecular sieve membrane prepared in example 1;

FIG. 7 is a surface SEM image of a SAPO-34 molecular sieve membrane prepared in comparative example 1.

Detailed Description

The invention is described in detail below with reference to the figures and specific embodiments. The present embodiment is implemented on the premise of the technical solution of the present invention, and a detailed implementation manner and a specific operation process are given, but the scope of the present invention is not limited to the following embodiments.

Example 1:

a method for synthesizing an SAPO-34 molecular sieve membrane based on microwave heating comprises the following steps:

(1) preparation of seed crystal coating liquid: pseudo-boehmite, deionized water, phosphoric acid and a template agent triethylamine are mixed according to the molar ratio of the components: p₂O₅/Al₂O₃1, templating agent/Al₂O₃＝2，H₂O/Al₂O₃Mixing the mixture at the temperature of 30 ℃, and stirring and aging the formed sol for 12 hours at normal temperature; the conventional SAPO-34 molecular sieve is pretreated into particles with the particle size of 500nm by adopting a mechanical crushing mode. An SEM image of SAPO-34 molecular sieve particles obtained by one-time mechanical crushing is shown in FIG. 4, and it can be seen that micron-sized molecular sieve grains are crushed into a nanometer grade after treatment; then adding the nanoscale SAPO-34 molecular sieve particles into the sol, and fully stirring to obtain a seed crystal coating liquid with the SAPO-34 molecular sieve content of 1 wt%.

(2) Treatment of the carrier and preparation of the seed layer: alpha-Al is added₂O₃Calcining the ceramic tube carrier at a high temperature of 650 ℃ for 2h, cooling, polishing the ceramic tube carrier by using 500-mesh sand paper, ultrasonically cleaning the ceramic tube carrier after polishing, and drying in a drying oven at a temperature of 200 ℃, wherein SEM images and cross-section SEM images of the surface and the cross-section of the ceramic tube carrier are respectively shown in figures 2 and 3, and it can be seen that the surface of the ceramic tube after treatment is still rough; taking the ceramic tube carrier out of the oven and then placing the ceramic tube carrier in the seed crystal coating liquid, vacuumizing the ceramic tube carrier at a negative pressure of 0.02Mpa for 30s, then placing the ceramic tube carrier in a microwave reactor and heating the ceramic tube carrier for 1h at 100 ℃, then placing the ceramic tube carrier in an oven and drying the ceramic tube carrier at 100 ℃, and obtaining a surface SEM image of the carrier containing the seed crystal layer as shown in figure 5, wherein the seed crystal and the coating liquid sol are filled into gaps on the surface of the carrier, and the seed crystal layer has a certain modification effect on the surface roughness of;

(3) molecular sieve membranePreparing a mother solution: weighing pseudo-boehmite, mixing the pseudo-boehmite in ionized water, adding phosphoric acid while stirring, and intensively stirring for 3 hours to completely hydrolyze the pseudo-boehmite and obtain a white milk-like uniform solution. Then adding silica sol, stirring for 1h at room temperature, adding a template agent triethylamine, stirring and aging for 24h, wherein the molar ratio of each component is as follows: p₂O₅/Al₂O₃＝1，SiO₂/Al₂O₃0.2, template/Al₂O₃＝1，H₂O/Al₂O₃＝150。

(4) Crystallization synthesis of molecular sieve membrane: sealing two ends of a pretreated carrier tube, vertically placing the carrier tube into a reaction kettle, then adding the molecular sieve membrane mother liquor into the reaction kettle, immersing the carrier in the molecular sieve membrane mother liquor, sealing, placing the carrier in a microwave reactor, standing and crystallizing for 24 hours at the self pressure of 200 ℃, wherein the heating rate is 3 ℃/min; and after crystallization, taking out the carrier, repeatedly washing the carrier for several times by using deionized water until the value of the solution is neutral, and then drying, roasting and removing the template agent to obtain the SAPO-34 molecular sieve membrane. Wherein the operation parameters of the template removing agent are as follows: heating from room temperature to 120 ℃, keeping the temperature at 120 ℃ for 2h, heating to 600 ℃, keeping the temperature for 2h, heating at the rate of 1 ℃/min, and then naturally cooling to room temperature.

The XRD spectrum of the prepared SAPO-34 molecular sieve membrane is shown in figure 1, and the SAPO-34 molecular sieve membrane is successfully prepared by adopting the method disclosed by the invention.

Example 2:

a method for synthesizing an SAPO-34 molecular sieve membrane based on microwave heating comprises the following steps:

(1) preparation of seed crystal coating liquid: the preparation process is basically the same as that of the step (1) in the example 1, except that the raw materials of the aluminum source, the phosphoric acid, the template agent and the deionized water are as follows according to the molar ratio of the components: p₂O₅/Al₂O₃1, templating agent/Al₂O₃＝3，H₂O/Al₂O₃When the concentration of the SAPO-34 molecular sieve in the seed crystal coating liquid is 50 percent, the template agent is tetraethylammonium hydroxide, and the content of the SAPO-34 molecular sieve in the seed crystal coating liquid is 0.5 percent by weight;

(2) treatment of the carrier and preparation of the seed layer: the preparation process was substantially the same as in step (2) of example 1, except that the support was calcined at 700 ℃ and the support coated with the seed layer was heated in a microwave reactor at 120 ℃ for 0.5 h;

(3) preparing a molecular sieve membrane mother solution: the preparation process is basically the same as that of the step (3) in the example 1, except that tetraethylammonium hydroxide is used as a template agent, and the template agent is stirred and aged for 12 hours, wherein the molar ratio of the components is as follows: p₂O₅/Al₂O₃＝1，SiO₂/Al₂O₃0.25% of templating agent/Al₂O₃＝1.5，H₂O/Al₂O₃＝100。

(4) Crystallization synthesis of molecular sieve membrane: the preparation process is basically the same as that of the step (4) in the example 1, except that the standing crystallization is carried out for 12 hours at 200 ℃.

Example 3:

a method for synthesizing an SAPO-34 molecular sieve membrane based on microwave heating comprises the following steps:

(1) preparation of seed crystal coating liquid: the preparation process is basically the same as that of the step (1) in the example 1, except that the raw materials of the aluminum source, the phosphoric acid, the template agent and the deionized water are as follows according to the molar ratio of the components: p₂O₅/Al₂O₃1, templating agent/Al₂O₃＝3.5，H₂O/Al₂O₃And (4) selecting triethylamine and tetraethylammonium hydroxide as the template agent according to the mole number of 1:1, mixing, wherein the content of the SAPO-34 molecular sieve in the seed crystal coating liquid is 1.5 wt%;

(2) treatment of the carrier and preparation of the seed layer: the preparation process was substantially the same as in step (2) of example 1, except that the support was calcined at 650 ℃ and the support coated with the seed layer was heated in a microwave reactor at 120 ℃ for 2 hours;

(3) preparing a molecular sieve membrane mother solution: the preparation process is basically the same as that of the step (3) in the example 1, except that the template agent is triethylamine and tetraethylammonium hydroxide in a molar ratio of 1:1, mixing, stirring and aging for 18h, wherein the molar ratio of each component is as follows: p₂O₅/Al₂O₃＝1，SiO₂/Al₂O₃0.3, template/Al₂O₃＝2，H₂O/Al₂O₃＝70。

(4) Crystallization synthesis of molecular sieve membrane: the preparation process is basically the same as that of the step (4) in the example 1, except that the standing crystallization is carried out for 18 hours at 200 ℃.

Example 4:

a method for synthesizing an SAPO-34 molecular sieve membrane based on microwave heating comprises the following steps:

(1) preparing seed crystals: the preparation process is basically the same as that of the step (1) in the example 1, except that the raw materials of the aluminum source, the phosphoric acid, the template agent and the deionized water are as follows according to the molar ratio of the components: p₂O₅/Al₂O₃1.5, template/Al₂O₃＝3.5，H₂O/Al₂O₃The aluminum source is aluminum isopropoxide, and the content of the SAPO-34 molecular sieve in the seed crystal coating liquid is 1.5 wt%.

(2) Treatment of the carrier and preparation of the seed layer: the preparation process was substantially the same as in step (2) of example 1, except that the support was calcined at 450 ℃ and the support coated with the seed layer was heated in a microwave reactor at 130 ℃ for 2 hours;

(3) preparing a molecular sieve membrane mother solution: the preparation process is basically the same as that of the step (3) in the embodiment 1, except that an aluminum source is aluminum isopropoxide, a silicon source is tetraethoxysilane, and the mixture is stirred and aged for 36 hours, wherein the molar ratio of the components is as follows: p₂O₅/Al₂O₃＝1，SiO₂/Al₂O₃0.25% of templating agent/Al₂O₃＝1.2，H₂O/Al₂O₃＝120。

(4) Crystallization synthesis of molecular sieve membrane: the preparation process is basically the same as that of the step (4) in the example 1, except that the standing crystallization is carried out for 14 hours at 200 ℃.

Example 5:

a method for synthesizing an SAPO-34 molecular sieve membrane based on microwave heating comprises the following steps:

(1) preparing seed crystals: the preparation process was substantially the same as in step (1) of example 1, except that the aluminum source was SB powder and the SAPO-34 molecular sieve content in the seed crystal coating liquid was 2 wt%.

(2) Treatment of the carrier and preparation of the seed layer: the preparation process was substantially the same as in step (2) of example 1, except that the support was calcined at 450 ℃ and the support coated with the seed layer was heated in a microwave reactor at 130 ℃ for 0.5 h.

(3) Preparing a molecular sieve membrane mother solution: the preparation process is basically the same as that of the step (3) in the embodiment 1, except that an aluminum source is SB powder, a silicon source is tetramethyl orthosilicate, and the preparation process is stirred and aged for 60 hours, wherein the molar ratio of the components is as follows: p₂O₅/Al₂O₃＝1，SiO₂/Al₂O₃0.4, template/Al₂O₃＝1.2，H₂O/Al₂O₃＝170。

(4) Crystallization synthesis of molecular sieve membrane: the preparation process is basically the same as that of the step (4) in the example 1, except that the standing crystallization is carried out for 16 hours at 190 ℃.

Example 6:

a method for synthesizing an SAPO-34 molecular sieve membrane based on microwave heating comprises the following steps:

(1) preparing seed crystals: the preparation process is basically the same as that of the step (1) in the example 1, except that SB powder is used as an aluminum source, tetraethylammonium hydroxide is used as a template agent, and the content of the SAPO-34 molecular sieve in the seed crystal coating liquid is 2 wt%.

(2) Treatment of the carrier and preparation of the seed layer: the preparation process was substantially the same as in step (2) of example 1, except that the support was sanded with 400 mesh sandpaper and then calcined at 750 ℃ and the support coated with the seed layer was heated in a microwave reactor at 130 ℃ for 0.5 h.

(3) Preparing a molecular sieve membrane mother solution: the preparation process is basically the same as that of the step (3) in the embodiment 1, except that an aluminum source is SB powder, a silicon source is tetramethyl orthosilicate, a template agent is tetraethylammonium hydroxide, the stirring and aging are carried out for 60 hours, and the molar ratio of the components is as follows: p₂O₅/Al₂O₃＝1，SiO₂/Al₂O₃0.23, template/Al₂O₃＝2，H₂O/Al₂O₃＝130。

(4) Crystallization synthesis of molecular sieve membrane: the preparation process was substantially the same as in the step (4) of example 1, except that the crystallization was carried out at 200 ℃ for 10 hours.

Example 7:

a method for synthesizing an SAPO-34 molecular sieve membrane based on microwave heating comprises the following steps:

(1) preparing seed crystals: the preparation process is basically the same as that in the step (1) in the embodiment 1, except that tetraethylammonium hydroxide is used as a template agent, and the conventional SAPO-34 molecular sieve is pretreated into particles with the particle size of 200-400nm in an acid-base treatment mode; the content of the SAPO-34 molecular sieve in the seed crystal coating liquid is 2 wt%;

(2) treatment of the carrier and preparation of the seed layer: the preparation process is basically the same as that of the step (2) in the example 1, except that the carrier is polished by 300-mesh sand paper, then calcined at 750 ℃ and heated in a microwave reactor at 90 ℃ for 1.5 h;

(3) preparing a molecular sieve membrane mother solution: the preparation process is basically the same as the step (3) in the embodiment 1, except that an aluminum source is pseudo-boehmite, a silicon source is tetraethyl orthosilicate, a template agent is tetraethylammonium hydroxide, and the stirring and aging are carried out for 24 hours, wherein the molar ratio of each component is as follows: p₂O₅/Al₂O₃＝1，SiO₂/Al₂O₃0.27% of templating agent/Al₂O₃＝2.5，H₂O/Al₂O₃＝90。

(4) Crystallization synthesis of molecular sieve membrane: the preparation process was substantially the same as in the step (4) of example 1, except that the crystallization was carried out at 185 ℃ for 8 hours.

Example 8:

a method for synthesizing an SAPO-34 molecular sieve membrane based on microwave heating comprises the following steps:

1) preparation of seed crystal coating liquid: mixing an aluminum source, phosphoric acid, a template agent and water to form sol, then stirring and aging at normal temperature, adding SAPO-34 molecular sieve particles, and stirring to obtain a seed crystal coating liquid;

2) preparing a seed crystal layer: pretreating a carrier, placing the pretreated carrier in seed crystal coating liquid, performing vacuum suction, placing the carrier in a microwave reactor for microwave heating, and drying to obtain a carrier containing a seed crystal layer;

3) crystallization synthesis of molecular sieve membrane: and (3) placing the carrier containing the seed crystal layer in a reaction kettle, adding the molecular sieve membrane mother liquor into the reaction kettle, then heating and crystallizing in a microwave reactor, washing, drying, and removing the template agent to obtain the SAPO-34 molecular sieve membrane.

In step 1), Al is contained in the sol₂O₃、P₂O₅Template and H₂The molar ratio of O is 1:1:4: 15; the stirring and aging time is 14 h. The grain size of SAPO-34 molecular sieve particles is 10-50 nm; in the seed crystal coating liquid, the content of SAPO-34 molecular sieve particles is 2 wt%.

In the step 2), the carrier is alpha-Al₂O₃A ceramic tube carrier; the pretreatment process comprises the following steps: calcining the carrier at 350 ℃ for 1.5h, cooling, polishing the carrier by 500-mesh sand paper, cleaning, and drying in an oven at 150 ℃ for 2.5 h. In the vacuum suction process, the pressure is 0.03MPa and the time is 25 s. In the microwave heating process, the temperature is 150 ℃ and the time is 0.5 h.

In the step 3), the preparation process of the molecular sieve membrane mother liquor comprises the following steps: adding an aluminum source into water, stirring and wetting, then adding phosphoric acid, fully hydrolyzing, then adding a silicon source and a template agent to form sol, stirring and aging at room temperature for 4 days to obtain a molecular sieve membrane mother solution; in sol, Al₂O₃、P₂O₅、SiO₂Template and H₂The molar ratio of O is 1:1:0.05:4: 15.

The temperature-rising crystallization process comprises the following steps: the temperature is increased from room temperature to 220 ℃ for crystallization, the temperature rising rate is 2.5 ℃/min, and the crystallization time is 26 h. The template agent removing process comprises the following steps: heating from room temperature to 110 deg.C, maintaining for 2.5h, heating to 580 deg.C, maintaining for 2.5h, and heating rate of 0.8 deg.C/min.

In this embodiment, the aluminum source includes pseudoboehmite and aluminum isopropoxide; the silicon source is tetrabutyl orthosilicate; the template agent comprises triethylamine and diethylamine.

Example 9:

a method for synthesizing an SAPO-34 molecular sieve membrane based on microwave heating comprises the following steps:

1) preparation of seed crystal coating liquid: mixing an aluminum source, phosphoric acid, a template agent and water to form sol, then stirring and aging at normal temperature, adding SAPO-34 molecular sieve particles, and stirring to obtain a seed crystal coating liquid;

2) preparing a seed crystal layer: pretreating a carrier, placing the pretreated carrier in seed crystal coating liquid, performing vacuum suction, placing the carrier in a microwave reactor for microwave heating, and drying to obtain a carrier containing a seed crystal layer;

3) crystallization synthesis of molecular sieve membrane: and (3) placing the carrier containing the seed crystal layer in a reaction kettle, adding the molecular sieve membrane mother liquor into the reaction kettle, then heating and crystallizing in a microwave reactor, washing, drying, and removing the template agent to obtain the SAPO-34 molecular sieve membrane.

In step 1), Al is contained in the sol₂O₃、P₂O₅Template and H₂The molar ratio of O is 1:2:0.15: 50; the stirring and aging time is 10 h. The particle size of the SAPO-34 molecular sieve particles is 550-600 nm; in the seed crystal coating liquid, the content of SAPO-34 molecular sieve particles is 0.5 wt%.

In the step 2), the carrier is alpha-Al₂O₃A ceramic tube carrier; the pretreatment process comprises the following steps: calcining the carrier at 750 ℃ for 2.5h, cooling, polishing the carrier by using 300-mesh sand paper, cleaning, and drying in an oven at 200 ℃ for 1.5 h. In the vacuum suction process, the pressure is 0.01MPa and the time is 35 s. In the microwave heating process, the temperature is 80 ℃ and the time is 3 h.

In the step 3), the preparation process of the molecular sieve membrane mother liquor comprises the following steps: adding an aluminum source into water, stirring and wetting, then adding phosphoric acid, fully hydrolyzing, then adding a silicon source and a template agent to form sol, stirring and aging at room temperature for 0.5 days to obtain a molecular sieve membrane mother liquor; in sol, Al₂O₃、P₂O₅、SiO₂Template and H₂The molar ratio of O is 1:2:0.5:0.15: 200.

The temperature-rising crystallization process comprises the following steps: the temperature is increased from room temperature to 150 ℃ for crystallization, the temperature rising rate is 3.5 ℃/min, and the crystallization time is 8 h. The template agent removing process comprises the following steps: heating from room temperature to 130 deg.C, maintaining for 1.5h, heating to 620 deg.C, maintaining for 1.5h, and heating rate is 1.2 deg.C/min.

In this embodiment, the aluminum source includes SB powder and aluminum hydroxide; the silicon source comprises tetraethyl orthosilicate and tetrapropyl orthosilicate; the template agent comprises tourmaline.

Example 10:

a method for synthesizing an SAPO-34 molecular sieve membrane based on microwave heating comprises the following steps:

1) preparation of seed crystal coating liquid: mixing an aluminum source, phosphoric acid, a template agent and water to form sol, then stirring and aging at normal temperature, adding SAPO-34 molecular sieve particles, and stirring to obtain a seed crystal coating liquid;

2) preparing a seed crystal layer: pretreating a carrier, placing the pretreated carrier in seed crystal coating liquid, performing vacuum suction, placing the carrier in a microwave reactor for microwave heating, and drying to obtain a carrier containing a seed crystal layer;

3) crystallization synthesis of molecular sieve membrane: and (3) placing the carrier containing the seed crystal layer in a reaction kettle, adding the molecular sieve membrane mother liquor into the reaction kettle, then heating and crystallizing in a microwave reactor, washing, drying, and removing the template agent to obtain the SAPO-34 molecular sieve membrane.

In step 1), Al is contained in the sol₂O₃、P₂O₅Template and H₂The molar ratio of O is 1:1.5:2: 35; the stirring and aging time is 12 h. The particle size of SAPO-34 molecular sieve particles is 300-350 nm; in the seed crystal coating liquid, the content of SAPO-34 molecular sieve particles is 1 wt%.

In the step 2), the carrier is alpha-Al₂O₃A ceramic tube carrier; the pretreatment process comprises the following steps: calcining the carrier at 500 ℃ for 2h, cooling, polishing the carrier by 400-mesh sand paper, cleaning, and drying in an oven at 170 ℃ for 2 h. In the vacuum suction process, the pressure is 0.02Mpa and the time is 30 s. In the microwave heating process, the temperature is 120 ℃ and the time is 2 h.

In the step 3), the preparation process of the molecular sieve membrane mother liquor comprises the following steps: adding an aluminum source into water, stirring and wetting, then adding phosphoric acid, fully hydrolyzing, then adding a silicon source and a template agent to form sol, stirring and aging at room temperature for 2 days to obtain a molecular sieve membrane mother solution; in sol, Al₂O₃、P₂O₅、SiO₂Template and H₂Molar ratio of OIs 1:1.5:0.3:2: 120.

The temperature-rising crystallization process comprises the following steps: heating from room temperature to 180 ℃ for crystallization, wherein the heating rate is 3 ℃/min, and the crystallization time is 16 h. The template agent removing process comprises the following steps: heating from room temperature to 120 ℃, then preserving heat for 2h, then heating to 600 ℃, then preserving heat for 2h, wherein the heating rate is 1 ℃/min.

In this example, the aluminum source was alumina; the silicon source comprises silica sol and tetramethyl orthosilicate; the template agent comprises tetraethyl ammonium hydroxide and tetrapropyl ammonium bromide.

Comparative example 1:

a method for hydrothermally synthesizing a SAPO-34 molecular sieve membrane comprises the following steps:

(1) preparation of seed crystal coating liquid: the preparation process is basically the same as that of step (1) of example 1, except that the conventional SAPO-34 molecular sieve is pretreated into particles with the particle size of 600 nm; then adding nanoscale SAPO-34 molecular sieve particles into ethanol, and fully dispersing to obtain a solution with the SAPO-34 molecular sieve content of 2 wt%.

(2) Treatment of the carrier and preparation of the seed layer: the preparation process is basically the same as the step (2) in the example 1, except that the carrier is calcined at 750 ℃ for 2 hours, then is ground by 300-mesh sand paper, is ultrasonically cleaned, and is dried in an oven at 150 ℃ for 2 hours; and taking the ceramic tube carrier out of the oven, then placing the ceramic tube carrier in the seed crystal coating liquid, vacuumizing the ceramic tube carrier for 30s under the negative pressure of 0.02Mpa, and then placing the ceramic tube carrier in the oven to heat the ceramic tube carrier for 1h at the temperature of 100 ℃ to obtain the carrier containing the seed crystal layer.

(3) Preparing a molecular sieve membrane mother solution: the preparation process is basically the same as the step (3) in the embodiment 1, except that an aluminum source is pseudo-boehmite, a silicon source is tetraethyl orthosilicate, a template agent is tetraethylammonium hydroxide, and the stirring and aging are carried out for 24 hours, wherein the molar ratio of each component is as follows: p₂O₅/Al₂O₃＝1，SiO₂/Al₂O₃0.27% of templating agent/Al₂O₃＝2.5，H₂O/Al₂O₃＝90。

(4) Crystallization synthesis of molecular sieve membrane: the preparation process is basically the same as that of the step (4) in the example 1, except that a hydrothermal synthesis mode is adopted, two ends of the carrier loaded with the seed crystal layer are sealed, the carrier is vertically placed into a reaction kettle, then the molecular sieve membrane mother liquor is added into the reaction kettle, the carrier is immersed in the molecular sieve membrane mother liquor, the carrier is placed into a reactor after sealing, and standing and crystallizing are carried out for 22 hours at 185 ℃.

Comparative example 2:

a method for synthesizing an SAPO-34 molecular sieve membrane based on microwave heating comprises the following steps:

(1) preparation of seed crystal coating liquid: adding pseudo-boehmite, deionized water, phosphoric acid and template tetraethylammonium hydroxide in sequence, stirring and mixing, wherein the molar ratio of the components is as follows: p₂O₅/Al₂O₃1, templating agent/Al₂O₃＝3，H₂O/Al₂O₃Stirring and aging the formed sol at normal temperature for 12 h; pretreating a conventional SAPO-34 molecular sieve into particles with the particle size of 600 nm; then adding nanoscale SAPO-34 molecular sieve particles into the sol, and fully stirring to obtain a solution with the SAPO-34 molecular sieve content of 2 wt%.

(2) Treatment of the carrier and preparation of the seed layer: the preparation process was substantially the same as in step (2) of example 1, except that the carrier was calcined at 650 ℃ and the seed-coated carrier was dried directly in an oven at 100 ℃ without microwave heating.

(3) Preparing a molecular sieve membrane mother solution: the preparation process is basically the same as that of the step (3) in the example 1, except that tetraethylammonium hydroxide is used as a template agent, and the template agent is stirred and aged for 18 hours, wherein the molar ratio of the components is as follows: p₂O₅/Al₂O₃＝1，SiO₂/Al₂O₃0.3, template/Al₂O₃＝2，H₂O/Al₂O₃＝70。

(4) Crystallization synthesis of molecular sieve membrane: the preparation process is basically the same as that of the step (4) in the example 1, except that the hydrothermal synthesis is adopted, the two ends of the carrier loaded with the seed crystal layer are sealed, the carrier is placed in a reaction kettle, the molecular sieve membrane mother solution in the step (3) is poured into the reaction kettle, the carrier is completely immersed and sealed, and the carrier is placed at 200 ℃ for standing and crystallization for 18 hours.

FIG. 6 is an SEM image of the surface (a) and cross section (b) of a SAPO-34 molecular sieve membrane prepared in example 1; FIG. 7 shows a graph of a comparative example 1And (3) SEM image of the surface of the prepared SAPO-34 molecular sieve membrane. As can be seen from the comparison of FIGS. 6 and 7, the SAPO-34 molecular sieve membrane synthesized by microwave heating has a flat surface and a uniform membrane thickness, while the SAPO-34 molecular sieve membrane synthesized by hydrothermal synthesis has different degrees of molecular sieve grain accumulation at each part and uneven membrane surface. Table 1 shows CO of SAPO-34 molecular sieve membranes prepared in examples 1-9 and comparative examples 1-2₂Gas permeability and CO₂/CH₄(50/50) separation Performance (25 ℃ C., feed pressure 0.3MPa) results show that SAPO-34 molecular sieve membranes synthesized by microwave heating all have good CO₂/CH₄Separation selectivity, and hydrothermal synthesis of SAPO-34 molecular sieve membrane CO₂High permeability, CO₂/CH₄The separation selectivity is poor due to uneven thickness of a molecular sieve membrane of hydrothermal synthesis and crack generation during high-temperature activation.

TABLE 1

The embodiments described above are described to facilitate an 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.