SSZ-39 molecular sieve membrane and preparation method thereof

Abstract

The invention provides an SSZ-39 molecular sieve membrane and a preparation method thereof, and belongs to the field of molecular sieve membrane preparation. The molecular sieve membrane is composed of an SSZ-39 molecular sieve crystal membrane layer with a selective separation function and a supporting body playing a supporting role, and the crystal membrane layer grows on the surface of the supporting body. The synthesis process of the membrane comprises the following steps: preparing a seed crystal, loading a seed crystal layer on a support body, carrying out hydrothermal secondary growth to form the membrane and activating a de-template agent. The prepared novel SSZ-39 molecular sieve membrane has high gas separation performance, can be used for separating mixed gases such as H2 / CH4, CO2 / CH4, CO2 / N2 and N2 / CH4, and has a good application prospect.

Description

Technical Field

[0001] The invention provides a method for preparing an SSZ-39 molecular sieve membrane, and belongs to the field of molecular sieve membrane material preparation and application. Background Art

[0002] Zeolite molecular sieve membrane is a kind of thin film material formed by the cross-linked growth of zeolite molecular sieve crystals on a porous carrier. It can be used in gas separation, liquid separation and membrane catalytic reaction and other fields, and has broad application value. Molecular sieve membrane is mainly prepared by hydrothermal secondary growth method, and the seed layer on the support body induces the formation of a continuous and dense molecular sieve membrane layer. According to its topological structure classification, common molecular sieve membranes are mainly divided into A type, Y type, MFI type, CHA type and DDR type. SSZ-39 molecular sieve is a silicon-aluminum molecular sieve with AEI topological structure. It has a three-dimensional pore with a diameter of 3.8 Å, which can be used for gas adsorption and catalytic reaction. It is also an ideal material for preparing molecular sieve membranes. SSZ-39 molecular sieve is made into a new separation membrane material, which can be used in gas separation systems such as carbon dioxide capture and hydrogen separation. SSZ-39 molecular sieve and its synthesis method were first disclosed by Zones et al. (US-5958370), using piperidinyl quaternary ammonium salt as a template and USY molecular sieve for crystallization synthesis. At present, the synthesis of SSZ-39 molecular sieve crystals is still very difficult. Usually, USY molecular sieve is required as all or part of the silicon and aluminum sources, and the product is also very easy to form other molecular sieve impurities, such as MOR, GME and GIS (Chem. Mater. 2020, 32, 60-74). SSZ-39 molecular sieve has a suitable pore size and is an ideal choice for the preparation of separation membrane materials. Tan et al. used SSZ-39 as a filler to prepare mixed matrix membranes for CO 2 / CH 4 The separation selectivity reaches 423 (Science, 2022, 378, 1189-1194). The direct synthesis of SSZ-39 molecular sieve membranes on porous carriers can achieve higher gas separation performance. Molecular sieve membranes require continuous and dense crystals on the membrane surface without impurities. In the case of high difficulty in synthesizing molecular sieve crystals, the synthesis of molecular sieve membranes is very challenging. There is currently no report on the synthesis and gas separation application of SSZ-39 molecular sieve membranes. Summary of the invention

[0003] In view of this, the object of the present invention is to provide a new high-performance SSZ-39 molecular sieve membrane material and a preparation method thereof. The SSZ-39 molecular sieve membrane material prepared by the present invention can be used for H 2 / CH 4 , CO 2 / CH 4 , CO 2 / N2 and N 2 / CH 4 Separation of mixed gases.

[0004] In order to achieve the above-mentioned object and other related objects, the present invention provides a SSZ-39 molecular sieve membrane and a preparation method thereof, characterized in that the method comprises the following steps: (1) Preparation of SSZ-39 molecular sieve seed crystals: The template (SDA), sodium hydroxide, silicon source, aluminum source, USY molecular sieve and water are mixed to obtain a sol, and the molar ratio of the active ingredients of the sol is: Al 2 O 3 / SiO 2 =0.01~0.1,SDA / SiO 2 = 0.1~1.0, NaOH / SiO 2 =0.1~1.0, H 2 O / SiO 2 =10~50; the above sol is hydrothermally reacted at 130~200 °C for 1~7 days, the product is centrifuged and washed, then dried at 60~100 °C, and finally calcined at 450~650 °C for 4~10 hours with a heating / cooling rate of 1 °C / min to obtain SSZ-39 molecular sieve seed crystals.

[0005] (2) Loading SSZ-39 molecular sieve seed crystals on a support to obtain a seeded support.

[0006] (3) Preparation of SSZ-39 molecular sieve membrane: The template agent (SDA), alkali source (MOH), silicon source, aluminum source and water are mixed to form a membrane synthesis sol, the molar ratio of the active ingredients is: Al 2 O 3 / SiO 2 =0~0.2,SDA / SiO 2 =0.05~2.0, MOH / SiO 2 =0.05~2.5, H 2 O / SiO 2 =10~200; after the sol is stirred and aged for 2~48 hours, it is transferred to a reactor, and the seed support obtained in step (2) is placed therein, followed by a hydrothermal reaction at 130~220°C for 0.5~7 days to form a membrane layer; after washing, drying and activation with a demolding agent, an SSZ-39 molecular sieve membrane is obtained.

[0007] Furthermore, in the above step (2), the material of the support body includes ceramic, stainless steel, mullite, alumina, titanium oxide, zirconium oxide, silicon dioxide or silicon carbide, and the shape includes flat plate, hollow fiber, tubular or multi-channel.

[0008] Furthermore, in the above step (2), the SSZ-39 molecular sieve seed crystals can be loaded onto the support by rubbing, dipping, spin coating, spraying and vacuum coating.

[0009] Furthermore, in the above steps (1) and (3), the aluminum source includes one or more of aluminum hydroxide, aluminum sulfate, metallic aluminum, aluminum isopropoxide, aluminum sec-butoxide, sodium aluminate and pseudo-boehmite.

[0010] Furthermore, in the above steps (1) and (3), the silicon source includes one or more of silica sol, silicon powder, silicate or sodium silicate.

[0011] Furthermore, the alkali source in the above step (3) includes sodium hydroxide or a mixture of sodium hydroxide and potassium hydroxide.

[0012] Furthermore, in the above steps (1) and (3), the template agent includes one or more of N,N-dimethyl-3,5-dimethylpiperidinium hydroxide, N,N-diethyl-2,6-dimethylpiperidinium hydroxide, tetraethylphosphine hydroxide, tetrapropylphosphine hydroxide, tetrabutylphosphine hydroxide and tetraethylammonium hydroxide.

[0013] Furthermore, in the above step (3), the SSZ-39 molecular sieve membrane release template activation is performed by high temperature calcination activation or ozone activation. The high temperature calcination temperature is 450-650°C, the time is 4-10 hours, and the heating / cooling rate is 0.1-0.5°C / min; the ozone activation temperature is 100-300°C, the treatment time is 2-10 days, and the heating / cooling rate is 1°C / min.

[0014] The novel SSZ-39 molecular sieve membrane synthesized by the present invention can be used for H 2 / CH 4 , CO 2 / CH 4 , CO 2 / N 2 and N 2 / CH 4 Separation of small molecule gas mixtures. 2 / CH 4 Separation selectivity greater than 10, CO 2 / CH 4 Separation selectivity greater than 100, CO 2 / N 2 Separation selectivity greater than 30, N 2 / CH 4 The separation selectivity is greater than 10. Beneficial Effects

[0015] The present invention provides a novel high-performance SSZ-39 molecular sieve membrane and a preparation method thereof. The synthesis of the membrane is simple. The SSZ-39 molecular sieve membrane has good gas separation performance and can be used for H 2 / CH 4 , CO 2 / CH 4 , CO 2 / N 2 and N 2 / CH 4 It can be used for separation of mixed gases and has good application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is the XRD pattern of the SSZ-39 molecular sieve seed crystal in Example 1.

[0017] Figure 2 1 is the XRD diagram of the SSZ-39 molecular sieve membrane in Examples 1 to 5.

[0018] Figure 3 Surface and cross-sectional SEM images of the SSZ-39 molecular sieve membrane prepared in Example 1.

[0019] Figure 4 This is a graph of the single gas permeation rate of the SSZ-39 molecular sieve membrane prepared in Example 1. DETAILED DESCRIPTION

[0020] To further describe the present invention, specific implementation examples are given below, but the patent rights are not limited to these examples. Example 1

[0021] The method for preparing the SSZ-39 molecular sieve membrane of the present invention is as follows: Step 1: Preparation of SSZ-39 molecular sieve seed crystals. Mix N,N-dimethyl-3,5-dimethylpiperidinium hydroxide (TMPOH, 25wt%), sodium hydroxide, silica sol, aluminum hydroxide, USY molecular sieve and water to obtain a sol, the molar ratio of the active ingredients is: SiO 2 / Al 2 O 3 =60,SDA / SiO 2 = 0.17, NaOH / SiO 2 =0.4, H 2 O / SiO 2 =12. The above sol was poured into a reactor, and the hydrothermal reaction was performed at 160°C for 3 days. The product was centrifuged and washed, dried at 60°C, and then calcined at 500°C for 10 hours with a heating / cooling rate of 1°C / min to obtain SSZ-39 molecular sieve seed crystals; Step 2: Load the SSZ-39 molecular sieve seed crystals on a porous support. A porous alumina tube is selected as the support. After the support is cleaned and dried, the SSZ-39 molecular sieve seed crystals are coated on the outer wall of the support by the dipping and pulling method. Specifically, the seed crystals prepared in step (1) are dispersed in ethanol to form a 0.5 wt% SSZ-39 molecular sieve seed crystal suspension. The support is placed in the suspension for 30 seconds and then taken out at a uniform speed. After drying, a seeded support is obtained.

[0022] Step 3: Preparation of SSZ-39 molecular sieve membrane. Mix N,N-dimethyl-3,5-dimethylpiperidinium hydroxide, sodium hydroxide, aluminum hydroxide, silica sol and deionized water and stir evenly to form a sol, the molar ratio of the active ingredients is: Al 2 O 3 / SiO 2 =0.016,SDA / SiO 2 = 0.5, NaOH / SiO 2 =0.28, H 2 O / SiO 2 =25; after the above sol is stirred and aged for 2 hours, it is transferred to a reactor, and the seed support obtained in step (2) is placed in it, and then hydrothermally reacted at 160°C for 2 days; after the reaction is complete, the membrane tube is taken out, cleaned and dried.

[0023] Step 4: Removal of template agent. The synthesized membrane was placed in a muffle furnace for calcination to remove the template agent. The calcination temperature was 480 °C, the calcination time was 4 hours, and the heating / cooling rate was 0.1 °C / min to obtain an activated SSZ-39 molecular sieve membrane, which was marked as M1.

[0024] The XRD pattern of the synthesized SSZ-39 molecular sieve seed is shown in Figure 1 , indicating that the synthesized product is pure SSZ-39 molecular sieve with high crystallinity.

[0025] The XRD pattern of film M1 is shown in Figure 2 , indicating that the synthesized membrane is a pure SSZ-39 molecular sieve membrane with high crystallinity and no other impurities.

[0026] The surface and cross-sectional electron microscopy images of membrane M1 are shown in Figure 3 From the figure, it can be seen that the SSZ-39 molecular sieve film layer on the surface of the membrane is continuous and dense. EDX characterization results show that the Si / Al ratio of the membrane is 10.1.

[0027] The gas separation performance of the membrane is expressed by two parameters: gas permeability P and separation coefficient α. Gas permeability P represents the total amount of gas that passes through a unit area of ​​the membrane per unit time and unit pressure. P = N / (A×ΔP), and the unit is mol / (m 2s Pa), the separation coefficient α is used to evaluate the membrane separation efficiency, α=P A / P B .

[0028] Figure 4 For membrane M1, H 2 , CO 2 、N 2 , CH 4 And other SF 6 The gas permeability test results of SSZ-39 molecular sieve membrane are shown in the figure. The test temperature is 25℃ and the test pressure is 0.2 MPa. 2 and H 2 The membrane has preferential permeability, CO 2 / CH 4 , CO 2 / N 2 , H 2 / CH 4 、N 2 / CH 4 The ideal separation selectivities are 130, 11.3, 40.6 and 11.5, respectively. 6 The permeation rate exceeded the detection limit, indicating that the membrane layer had good density.

[0029] Use membrane M1 for CO 2 / CH 4 The separation performance of the membrane is shown in Table 1. At 25 °C and 0.2 MPa, the CO 2 The penetration rate is 9.5×10 -7 mol / (m 2 s Pa), CO 2 / CH 4 The selectivity is 620. Example 2

[0030] The operation steps adopted are the same as those in Example 1, except that in step 2, a porous mullite tube is used as a support for membrane synthesis, and the SSZ-39 molecular sieve seed is loaded on the support by a wiping method; in step 3, tetraethoxysilane is used as a silicon source, and no aluminum source is added, and the molar ratio of the effective ingredient in the synthetic sol is Al 2 O 3 / SiO 2 =0,SDA / SiO 2 = 0.35, NaOH / SiO 2 =0.65, H 2 O / SiO 2=40, aging time is 12 hours; in step 3, reaction temperature is 140 ℃, reaction time is 5 days; in step 4, membrane calcination temperature is 450 ℃, calcination time is 10 hours, heating / cooling rate is 0.5 ℃ / min. The synthesized SSZ-39 molecular sieve membrane is marked as M2.

[0031] The XRD pattern of film M2 is shown in Figure 2 , indicating that the synthesized membrane is a pure SSZ-39 molecular sieve membrane without impurities. 2 / CH 4 The test results of mixed gas separation performance are shown in Table 1. The test conditions are 0.2 MPa and 25 °C. Example 3

[0032] The operating steps used are the same as those in Example 1, except that in step 3, the silicon source used is silicon powder, the aluminum source is sodium aluminate, the template agent is a mixture of N,N-dimethyl-3,5-dimethylpiperidinium hydroxide and tetraethylphosphine hydroxide (molar ratio of 4:1), and the molar ratio of the membrane synthesis sol is: Al 2 O 3 / SiO 2 =0.01,SDA / SiO 2 =2.0, NaOH / SiO 2 =2.5, H 2 O / SiO 2 =200; in step 3, the reaction temperature is 200 °C and the reaction time is 1 day; in step 4, the template is removed by ozone activation treatment, the treatment temperature is 200 °C, the treatment time is 4 days, and the heating / cooling rate is 1 °C / min. The synthesized SSZ-39 molecular sieve membrane is marked as M3.

[0033] The XRD pattern of film M3 is shown in Figure 2 , indicating that the synthesized membrane is a pure SSZ-39 molecular sieve membrane without impurities. 2 / CH 4 The test results of mixed gas separation performance are shown in Table 1. The test conditions are 0.2 MPa and 25 °C. Example 4

[0034] The operating steps used are the same as those in Example 1, except that in step 3, the molar ratio of the membrane synthesis sol is: Al 2 O 3 / SiO 2 =0.1,SDA / SiO 2 = 0.05, NaOH / SiO 2 =0.28, H 2 O / SiO 2=10, sol aging for 24 hours; in step 4, the template agent is removed by ozone activation treatment, the treatment temperature is 300 °C, the treatment time is 2 days, and the heating / cooling rate is 1 °C / min. The synthesized SSZ-39 molecular sieve membrane is recorded as M4.

[0035] The XRD pattern of film M4 is shown in Figure 2 , indicating that the synthesized membrane is a pure SSZ-39 molecular sieve membrane without impurities. 2 / CH 4 The test results of mixed gas separation performance are shown in Table 1. The test conditions are 0.2 MPa and 25 °C. Example 5

[0036] The operating steps adopted are the same as those in Example 1, except that in step 3, the alkali source is a mixture of KOH and NaOH, the NaOH / KOH molar ratio is 9, the synthetic sol is aged for 48 hours, and the reaction is carried out at 130°C for 7 days; in step 4, the template agent is removed by ozone activation treatment, the treatment temperature is 100°C, the treatment time is 10 days, and the heating / cooling rate is 1°C / min. The synthesized SSZ-39 molecular sieve membrane is marked as M5.

[0037] The XRD pattern of film M5 is shown in Figure 2 , indicating that the synthesized membrane is a pure SSZ-39 molecular sieve membrane without impurities. 2 / CH 4 The test results of mixed gas separation performance are shown in Table 1. The test conditions are 0.2 MPa and 25 °C. Example 6

[0038] The operating steps used are the same as those in Example 1, except that in step 3, the molar ratio of the membrane synthesis sol is: Al 2 O 3 / SiO 2 =0.2, TMPOH / SiO 2 = 0.6, NaOH / SiO 2 =1,H 2 O / SiO 2 = 50. In step 4, the reaction was carried out at 160°C for 3 days. The synthesized SSZ-39 molecular sieve membrane was recorded as M6.

[0039] Membrane M6 CO 2 / CH 4 The test results of mixed gas separation performance are shown in Table 1. The test conditions are 0.2 MPa and 25 °C. Example 7

[0040] The operating steps adopted are the same as those in Example 1, except that in step 3, the aging time of the synthetic sol is 48 hours, the synthesis temperature of the membrane is 220°C, and the reaction time is 0.5 days; in step 4, the calcination temperature of the membrane is 650°C, and the heating / cooling rates are both 0.1°C / min. The synthesized SSZ-39 molecular sieve membrane is denoted as M7.

[0041] Membrane M7 CO 2 / CH 4 The test results of mixed gas separation performance are shown in Table 1. The test conditions are 0.2 MPa and 25 °C. Example 8

[0042] The operating steps adopted are the same as those in Example 1, except that in step 3, the aluminum source is aluminum isopropoxide, the alkali source is a mixture of KOH and NaOH, the NaOH / KOH molar ratio is 4, and the sol aging time is 12 hours; in step 4, the template agent is removed by ozone activation treatment, the treatment temperature is 200°C, the treatment time is 4 days, and the heating / cooling rate is 1°C / min. The synthesized SSZ-39 molecular sieve membrane is recorded as M4.

[0043] Membrane M8 CO 2 / CH 4 The test results of mixed gas separation performance are shown in Table 1. The test conditions are 0.2 MPa and 25 °C.

[0044] Table 1 CO of SSZ-39 molecular sieve membrane 2 / CH 4 (50 / 50) mixed gas separation performance (25 ℃, 0.2 MPa)

Claims

1. A SSZ-39 molecular sieve membrane and a preparation method thereof, characterized in that: The following steps are involved: (1) Preparation of SSZ-39 molecular sieve seed crystals: a template agent (SDA), sodium hydroxide, a silicon source, an aluminum source, a USY molecular sieve and water are mixed to obtain a sol, wherein the molar ratio of the effective components of the sol is: Al2O3 / SiO2=0.01~0.1, SDA / SiO2=0.1~1.0, NaOH / SiO2=0.1~1.0, H2O / SiO2=5~50; the above sol is hydrothermally reacted at 130~200°C for 1~7 days, the product is centrifuged and washed, dried at 60~100°C, and finally calcined at 450~650°C for 4~10 hours, with a heating / cooling rate of 1°C / min, to obtain SSZ-39 molecular sieve seed crystals; (2) loading SSZ-39 molecular sieve seed crystals on a support to obtain a seeded support; (3) Preparation of SSZ-39 molecular sieve membrane: a template agent (SDA), an alkali source (MOH), a silicon source, an aluminum source and water are mixed to form a membrane synthesis sol, wherein the molar ratio of the effective components is: Al2O3 / SiO2=0~0.2, SDA / SiO2=0.05~2.0, MOH / SiO2=0.05~2.5, H2O / SiO2=10~200; after the sol is stirred and aged for 2~48 hours, it is transferred to a reactor, and the seeded support obtained in step (2) is placed in it, and then hydrothermally reacted at 130~220°C for 0.5~7 days to form a membrane layer; after washing, drying and de-templating agent activation, the SSZ-39 molecular sieve membrane is obtained.

2. The SSZ-39 molecular sieve membrane and preparation method thereof according to claim 1, characterized in that: In the step (2), the material of the support body includes ceramic, stainless steel, mullite, alumina, titanium oxide, zirconium oxide, silicon dioxide or silicon carbide, and the shape includes flat plate, hollow fiber, tube or multi-channel.

3. The SSZ-39 molecular sieve membrane and preparation method thereof according to claim 1, characterized in that: In the step (2), the loading method of the SSZ-39 molecular sieve seed crystals includes rubbing, dipping, spin coating, spraying or vacuum coating.

4. The SSZ-39 molecular sieve membrane and the preparation method thereof according to claim 1, characterized in that: In the steps (1) and (3), the aluminum source used includes one or more of aluminum hydroxide, aluminum sulfate, metallic aluminum, aluminum isopropoxide, aluminum sec-butoxide, sodium aluminate or pseudo-boehmite.

5. The SSZ-39 molecular sieve membrane and preparation method thereof according to claim 1, characterized in that: In the steps (1) and (3), the silicon source includes one or more of silica sol, silicon powder, silicate or sodium silicate.

6. The SSZ-39 molecular sieve membrane and the preparation method thereof according to claim 1, characterized in that: In the step (3), the alkali source includes sodium hydroxide or a mixture of sodium hydroxide and potassium hydroxide.

7. The SSZ-39 molecular sieve membrane and the preparation method thereof according to claim 1, characterized in that: In the steps (1) and (3), the template agent includes one or more of N,N-dimethyl-3,5-dimethylpiperidinium hydroxide, N,N-diethyl-2,6-dimethylpiperidinium hydroxide, tetraethylphosphine hydroxide, tetrapropylphosphine hydroxide, tetrabutylphosphine hydroxide or tetraethylammonium hydroxide.

8. The SSZ-39 molecular sieve membrane and preparation method thereof according to claim 1, characterized in that: In the step (3), the SSZ-39 molecular sieve membrane release template activation is carried out by high temperature calcination activation or ozone activation; the high temperature calcination temperature is 450-650°C, the time is 4-10 hours, and the heating / cooling rate is 0.1-0.5°C / min; the ozone activation temperature is 100-300°C, the treatment time is 2-10 days, and the heating / cooling rate is 1°C / min.

Images