A method for preparing ERI-type zeolite molecular sieve membranes and its application

Abstract

This invention belongs to the field of membrane separation materials technology, and relates to a method for preparing ERI-type zeolite molecular sieve membranes and their applications. This method is green, environmentally friendly, simple, rapid, and economical. It eliminates the need for expensive organic template agents or environmentally harmful inorganic fluoride ions, resulting in low energy consumption and a simple, reproducible preparation process with a crystallization time of only 3-6 hours. The ERI-type zeolite molecular sieve membranes prepared by this invention exhibit excellent separation performance and good stability in the dehydration and purification of organic solvents such as acetic acid. The preparation process proposed in this invention is expected to provide a promising reference scheme for the preparation of high-performance zeolite membranes and possesses potential practical application feasibility.

Description

Technical Field

[0001] This invention belongs to the field of membrane separation materials technology, and relates to a method for preparing ERI-type zeolite molecular sieve membranes and their applications. Background Art

[0002] Acetic acid is one of the 50 most important chemicals in industry, widely used in the synthesis of compounds such as polyvinyl acetate, vinyl acetate, acetate esters, and chloroacetic acid. It is also an important industrial solvent and raw material used in textile printing and dyeing, photographic pharmaceutical manufacturing, and the rubber industry. Whether using the traditional methanol carbonyl synthesis method or biomass fermentation to produce acetic acid, the dehydration and purification of crude acetic acid is an essential unit process. Although water and acetic acid do not usually form an azeotrope, the presence of a tangential pinch point in acetic acid solutions typically necessitates multiple equilibrium stages in the distillation column and the use of high reflux ratios, leading to increased energy consumption. Traditional acetic acid dehydration methods, while mature and widely used, suffer from drawbacks such as high energy consumption, large equipment investment, and secondary pollution. Therefore, developing novel, environmentally friendly, and energy-efficient acetic acid dehydration and separation technologies is particularly important.

[0003] Pervaporation is a membrane separation technology used to separate liquid mixtures, selectively permeating water or organic compounds. Compared to traditional distillation, pervaporation overcomes the limitations of thermodynamic vapor-liquid equilibrium and requires only latent heat of vaporization, resulting in lower energy consumption. Pervaporation technology offers numerous advantages, including simple and flexible operation, low energy consumption, high separation efficiency, no introduction of other reagents, no need for secondary product processing, no secondary pollution, and ease of scale-up. It is particularly suitable for isomers, thermosensitive, near-boiling, and azeotropic systems that are difficult or impossible to separate using traditional methods, and is considered one of the most important and promising high-tech advancements in current industrial technological transformation.

[0004] Acetic acid is readily soluble in water, and the resulting miscible system is relatively stable, making it difficult to separate from water. Furthermore, acetic acid is highly corrosive, necessitating materials with high acid resistance. In the 21st century, microporous inorganic membranes emerged as a new generation of membrane materials for separating molecular mixtures under harsh conditions. The excellent acid resistance and tunable hydrophilicity of inorganic membranes make them highly promising for acetic acid dehydration. Zeolite molecular sieve membranes constitute the largest family of inorganic perevaporation membrane materials, possessing tunable hydrophilicity and sub-nanometer molecular sieve pores, providing strong preferential adsorption and rapid selective diffusion for efficient molecular separation.

[0005] The silica-to-alumina ratio of the zeolite molecular sieve membrane framework is one of the important factors determining the hydrophilicity and acid resistance of the membrane material. Generally, as the silica-to-alumina ratio of the zeolite membrane framework increases, the hydrophilicity of the membrane decreases and the acid resistance increases. According to the different silica-to-alumina ratios of molecular sieves, molecular sieve membranes can be divided into three categories: (1) low silica-to-alumina ratio, with a silica-to-alumina ratio of 1.0-1.5, such as NaA, NaY, etc.; (2) medium silica-to-alumina ratio, with a silica-to-alumina ratio of 2.0-5.0, such as CHA, ERI, and T-type zeolites (ERI / OFF symbiotic zeolites), etc.; (3) high silica-to-alumina ratio, with a silica-to-alumina ratio greater than 5.0, such as MOR, MFI, etc. MFI and MOR type zeolite membranes with high silica-to-alumina ratios can maintain good stability under high concentration and high temperature acidic conditions. Therefore, research on the application of zeolite membranes in acetic acid dehydration mainly focuses on MFI and MOR type zeolite membranes. However, the high silica-to-alumina ratio of MFI and MOR type zeolite membranes also limits the hydrophilicity of the membrane. This means that while MFI and MOR type zeolite membranes have excellent separation selectivity and acid / hydrothermal stability, there is still room for improvement in permeation flux.

[0006] Furthermore, the acid resistance and hydrophilicity of zeolite membranes also depend on their topology. Compared to mesoporous MFI and MOR type zeolite membranes, ERI type zeolites with small pores are eight-membered ring molecular sieves. Different topologies are expected to exhibit different acid resistance. ERI-configured molecular sieves can be divided into phosphorus aluminum type (AlPO-17 and SAPO-17) and silica aluminum type according to the different framework elements. The phosphorus aluminum type ERI molecular sieve framework is composed of Si, Al, P, and O atoms. The introduction of heteroatoms P makes it more conducive to CO2 adsorption, so it is often used as a CO2 adsorbent. On the other hand, silica aluminum type ERI molecular sieves are composed of Si, Al, and O atoms in the framework. Compared with phosphorus aluminum type ERI molecular sieves, the framework has a higher silicon content. The higher the framework silicon content, the stronger the acid resistance. Therefore, its acid resistance and hydrothermal stability are more stable. Moreover, silica aluminum type ERI zeolite molecular sieves have a medium silicon-to-aluminum ratio, which not only exhibits good acid resistance but also maintains excellent hydrophilicity. This allows them to achieve high permeation flux while also possessing good acid resistance, separation selectivity, and stability, making them suitable for dehydration separation applications in various organic solvent systems. Therefore, silica-alumina type ERI zeolite membranes (hereinafter referred to as ERI-type zeolite membranes) are also potentially ideal membrane materials for the dehydration and purification of organic solvents such as acetic acid. However, there are currently no reports on the preparation of ERI-type zeolite membranes for the dehydration and purification of organic solvents such as acetic acid. In addition, when designing the preparation process of ERI-type zeolite membranes, higher requirements are placed on the environmental protection, process complexity, and economic efficiency of the preparation process to ensure its feasibility and advantages in practical applications. Summary of the Invention

[0007] To address the aforementioned problems, this invention provides a green, environmentally friendly, simple, rapid, and economical method for preparing ERI-type zeolite molecular sieve membranes, and applies it to the dehydration of organic solvents such as acetic acid. The proposed method eliminates the need for expensive organic template agents or environmentally harmful inorganic fluoride ions, consumes little energy, is environmentally friendly, has a simple and easy-to-operate preparation process, high reproducibility, and a crystallization time of only 3-6 hours. The proposed preparation process provides a promising reference scheme for the preparation of high-performance zeolite membranes and possesses potential practical application feasibility.

[0008] A method for preparing an ERI-type zeolite molecular sieve membrane involves coating a porous support surface with T-type zeolite seed crystals to form a smooth and dense T-type zeolite seed crystal layer, preparing a synthesis solution, and then hydrothermally crystallizing the coated T-type zeolite seed crystal layer in the synthesis solution environment to form an ERI-type zeolite membrane. The specific steps are as follows:

[0009] Step (1) Coating the seed layer: Disperse two types of T-type zeolite seed crystals with different particle sizes in deionized water to obtain molecular sieve seed solution A and molecular sieve seed solution B; preheat the porous carrier at 150-200 ℃ for 2-5 h, and then coat the outer surface of the preheated porous carrier with molecular sieve seed solution A; cure at 150-200 ℃ for 2-12 h to obtain a smooth and dense seed layer A1; wipe off the loose seed crystals on the outer surface of seed layer A1 with degreased cotton; then preheat seed layer A1 at 80-120 ℃ for 2-5 h, and then coat the outer surface of the preheated seed layer A1 with molecular sieve seed solution B; cure at 80-120 ℃ for 2-12 h to obtain a smooth and dense T-type zeolite seed layer;

[0010] Step (2), preparing the synthesis solution: The synthesis solution is prepared from silicon source, aluminum source, alkali source and deionized water; the silicon source is silica sol; the aluminum source is sodium aluminate; the alkali source is a mixture of sodium hydroxide and potassium hydroxide; the aluminum source and alkali source are added to deionized water, stirred until clear, then the silicon source is added, and aged to form a stable SiO2-Na2O-K2O-Al2O3-H2O synthesis solution system;

[0011] Step (3), crystallization and film formation: The porous carrier coated with the T-type zeolite seed layer in step (1) is placed in the reactor, and the synthetic liquid that has been aged in step (2) is added to the reactor to completely immerse the porous carrier. After sealing the reactor, crystallization is performed to obtain the ERI type zeolite molecular sieve membrane.

[0012] In step (1), the mass fraction of T-type zeolite seeds in molecular sieve seed solution A is 1.0-2.0 wt.%, and the particle size of the T-type zeolite seeds is 1.0-2.0 μm; the mass fraction of T-type zeolite seeds in molecular sieve seed solution B is 0.2-1.0 wt.%, and the particle size of the T-type zeolite seeds is 0.05-0.6 μm.

[0013] In step (1), the method of coating the molecular sieve seed liquid onto the surface of the porous carrier is impregnation, hot impregnation, two-step variable temperature hot impregnation, vacuum crystal coating, wiping coating or spin coating; preferably, the two-step variable temperature hot impregnation method is used.

[0014] In step (2), the molar ratios of the components in the synthesis solution are as follows: the molar ratio of SiO2 to Al2O3 is (35-500):1; the molar ratio of H2O to SiO2 is (28-200):1; the molar ratio of Na2O to SiO2 is (0.3-1.5):1; the molar ratio of K2O to SiO2 is (0.01-0.3):1; the stirring and aging temperature is 10-40 ℃; and the aging time is 6-48 h.

[0015] In step (3), the crystallization temperature is 120-150 ℃ and the crystallization time is 3-6 h.

[0016] In steps (1) and (3), the porous carrier is in the shape of a tubular, flat, hollow fiber or porous carrier; preferably a tubular carrier.

[0017] In steps (1) to (3), the porous carrier is made of alumina, zirconium oxide, mullite, stainless steel or metal mesh; the pore size of the porous carrier is 0.02-40 μm; preferably alumina, and the pore size of the porous carrier is preferably 0.1-5 μm.

[0018] The ERI-type zeolite molecular sieve membrane prepared by the above method is used for organic solvent dehydration separation, wherein the organic solvent is acetic acid, ethanol, ethyl acetate or isopropanol.

[0019] The beneficial effects of this invention are:

[0020] (1) This invention proposes a method for preparing ERI-type zeolite molecular sieve membranes. This preparation method does not require the use of expensive organic template agents or environmentally harmful inorganic fluoride ions, and is energy-efficient and environmentally friendly.

[0021] (2) The preparation process is simple and easy to operate, highly repeatable, and the crystallization time is only 3-6 h, which makes the method of the present invention have excellent film-forming efficiency.

[0022] (3) The ERI-type zeolite molecular sieve membrane prepared by the method of the present invention exhibits excellent dehydration and separation performance for organic solvents such as acetic acid. Furthermore, the ERI-type zeolite molecular sieve membrane prepared by the present invention demonstrates good acid resistance while exhibiting high separation performance.

[0023] (4) This invention effectively saves membrane fabrication costs, significantly shortens the membrane fabrication cycle, and fully embodies the concept of green chemistry. The preparation process proposed in this invention is expected to provide a promising reference scheme for the preparation of high-performance zeolite membranes and has potential practical application feasibility. Attached Figure Description

[0024] Figure 1 The X-ray diffraction pattern of the ERI-type zeolite molecular sieve membrane synthesized in Example 1;

[0025] Figure 2 This is the X-ray diffraction pattern of the ERI-type zeolite molecular sieve membrane synthesized in Example 2;

[0026] Figure 3 This is a scanning electron microscope image of the surface of the ERI-type zeolite molecular sieve membrane synthesized in Example 3;

[0027] Figure 4 This is a cross-sectional scanning electron microscope image of the ERI-type zeolite molecular sieve membrane synthesized in Example 3;

[0028] Figure 5 The X-ray diffraction pattern of the ERI-type zeolite molecular sieve membrane synthesized in Example 3;

[0029] Figure 6 The pervaporation time stability of the ERI-type zeolite molecular sieve membrane synthesized in Example 3. Detailed Implementation

[0030] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings and technical solutions. Example

[0031] (1) The porous carrier tube was preheated at 175 °C for 3 h, and then quickly immersed in a T-type molecular sieve seed solution A with a mass concentration of 1.5 wt.% and a particle size of 1.5 μm. and cured at 175 °C for 3 h to obtain a seed layer A1; the seed on the surface of the carrier was wiped off with degreased cotton, the seed layer A1 was preheated at 100 °C for 3 h, and then immersed in a T-type molecular sieve seed solution B with a mass concentration of 0.2 wt.% and a particle size of 0.6 μm. and cured at 100 °C for 3 h to obtain a flat and dense T-type zeolite seed layer;

[0032] (2) Prepare a synthesis solution with a molar ratio of 1SiO2:0.01Al2O3:1.5Na2O:0.1K2O:200H2O, and stir and age it at 10 °C for 48 h;

[0033] (3) Seal both ends of the coated T-type seed layer carrier tube and place it vertically in the reactor. Add the aged synthesis liquid to the reactor so that it completely submerges the top of the carrier tube. After sealing the reactor, crystallize it at 130 °C for 4 h.

[0034] (4) The synthesized zeolite molecular sieve membrane was washed with deionized water until neutral and then dried in an oven at 50 °C.

[0035] Depend on Figure 1 It can be seen that the zeolite molecular sieve membrane prepared in this embodiment is a pure ERI zeolite crystalline phase. The ERI-type zeolite molecular sieve membrane prepared in this embodiment was subjected to pervaporation tests. At 60 °C and 90 °C, the fluxes for 90 wt.% acetic acid / water were 2.07 and 4.58 kg·m³, respectively. -2 ·h -1 The separation factors were all greater than 10,000. At 75 °C, the fluxes for 70 wt.%, 85 wt.%, and 90 wt.% acetic acid / water were 3.73, 3.03, and 2.82 kg·m⁻¹, respectively. -2 ·h -1 The separation factors were all greater than 10000. At 75 °C, the fluxes for 90 wt. % ethanol / water and 90 wt. % isopropanol / water were 3.81 and 5.43 kg·m⁻¹, respectively. -2 ·h -1 The separation factors are all greater than 10000. Example

[0036] (1) The porous carrier tube was preheated at 200 °C for 2 h, and then quickly immersed in a T-type molecular sieve seed solution A with a mass concentration of 2.0 wt.% and a particle size of 1.0 μm. and cured at 200 °C for 2 h to obtain a seed layer A1; the seed crystals on the surface of the carrier were wiped off with degreased cotton, and the seed layer A1 was preheated at 80 °C for 2 h, and then immersed in a T-type molecular sieve seed solution B with a mass concentration of 1.0 wt.% and a particle size of 0.05 μm. and cured at 80 °C for 2 h to obtain a flat and dense T-type zeolite seed layer;

[0037] (2) Prepare a synthesis solution with a molar ratio of 1SiO2:0.002Al2O3:0.3Na2O:0.3K2O:28H2O, and stir and age it at 40 °C for 6 h;

[0038] (3) Seal both ends of the coated T-type seed layer carrier tube and place it vertically in the reactor. Add the aged synthesis liquid to the reactor so that it completely submerges the top of the carrier tube. After sealing the reactor, crystallize it at 120 °C for 6 h.

[0039] (4) The synthesized zeolite molecular sieve membrane was washed with deionized water until neutral and then dried in an oven at 50 °C.

[0040] Depend on Figure 2 It can be seen that the main phase of the zeolite molecular sieve membrane prepared in this embodiment is ERI zeolite crystal phase, accompanied by a small amount of CHA zeolite crystal phase. The ERI-type zeolite molecular sieve membrane prepared in this embodiment was subjected to pervaporation tests. At 60 °C and 90 °C, the fluxes for 90 wt.% acetic acid / water were 1.81 and 3.98 kg·m³, respectively. -2 ·h -1 The separation factors were all greater than 10,000. At 75 °C, the fluxes for 70 wt.%, 85 wt.%, and 90 wt.% acetic acid / water were 3.29, 2.77, and 2.57 kg·m⁻¹, respectively. -2 ·h -1 The separation factors were all greater than 10,000. At 75 °C, the fluxes for 90 wt.% ethanol / water, 90 wt.% ethyl acetate / water, and 90 wt.% isopropanol / water were 3.46, 5.89, and 5.04 kg·m⁻¹, respectively. -2 ·h -1 The separation factors are all greater than 10000. Example

[0041] (1) The porous carrier tube was preheated at 150 °C for 5 h, and then quickly immersed in a T-type molecular sieve seed solution A with a mass concentration of 1.0 wt.% and a particle size of 2.0 μm. It was cured at 150 °C for 12 h to obtain a seed layer A1; the seed crystals on the surface of the carrier were wiped off with degreased cotton, and the seed layer A1 was preheated at 120 °C for 5 h, and then immersed in a T-type molecular sieve seed solution B with a mass concentration of 0.5 wt.% and a particle size of 0.4 μm. It was cured at 120 °C for 12 h to obtain a flat and dense T-type zeolite seed layer;

[0042] (2) Prepare a synthesis solution with a molar ratio of 1SiO2:0.028Al2O3:0.8Na2O:0.01K2O:100H2O, and stir and age it at 25 °C for 24 h;

[0043] (3) Seal both ends of the coated T-type seed layer carrier tube and place it vertically in the reactor. Add the aged synthesis liquid to the reactor so that it completely submerges the top of the carrier tube. After sealing the reactor, crystallize it at 150 °C for 3 h.

[0044] (4) The synthesized zeolite molecular sieve membrane was washed with deionized water until neutral and then dried in an oven at 50 °C.

[0045] Depend on Figure 3-5 It can be seen that the main phase of the zeolite molecular sieve membrane prepared in this embodiment is ERI zeolite crystal phase, accompanied by a small amount of CHA zeolite crystal phase. The ERI-type zeolite molecular sieve membrane prepared in this embodiment was subjected to pervaporation tests. At 60 °C and 90 °C, the fluxes for 90 wt.% acetic acid / water were 2.47 and 5.40 kg·m³, respectively. -2 ·h -1 The separation factors were all greater than 10000. At 75 °C, the fluxes for 70 wt.%, 85 wt.%, and 90 wt.% acetic acid / water were 4.40, 3.58, and 3.32 kg·m⁻², respectively. -2 ·h -1 The separation factors were all greater than 10,000. At 75 °C, the fluxes for 90 wt.% ethanol / water and 90 wt.% isopropanol / water were 4.48 and 6.39 kg·m⁻¹, respectively. -2 ·h -1 The separation factors are all greater than 10000.

[0046] Figure 6 The graph shows the stability of the ERI-type zeolite molecular sieve membrane prepared in this embodiment during the pervaporation time test of 90 wt.% acetic acid / water at 75 °C. As can be seen from the graph, the separation factor of the ERI-type zeolite molecular sieve membrane remained basically stable throughout the 154-hour pervaporation test, while the permeate flux initially decreased and then stabilized. The slight decrease in permeate flux may be due to acetic acid molecules being adsorbed on the membrane surface during the pervaporation separation process, occupying adsorption sites and preventing water molecules from permeating the membrane effectively. Throughout the pervaporation time stability test, the ERI-type zeolite molecular sieve membrane exhibited good stability.

Claims

1. A method for preparing an ERI-type zeolite molecular sieve membrane, characterized in that, The specific steps are as follows: Step (1) Coating the seed layer: Disperse two types of T-type zeolite seed crystals with different particle sizes in deionized water to obtain molecular sieve seed solution A and molecular sieve seed solution B; preheat the porous carrier at 150-200℃ for 2-5 hours, and then coat the outer surface of the preheated porous carrier with molecular sieve seed solution A; cure at 150-200℃ for 2-12 hours to obtain a smooth and dense seed layer A1; wipe off the loose seed crystals on the outer surface of seed layer A1 with degreased cotton; then preheat seed layer A1 at 80-120℃ for 2-5 hours, and then coat the outer surface of the preheated seed layer A1 with molecular sieve seed solution B; cure at 80-120℃ for 2-12 hours to obtain a T-type zeolite seed layer; Step (2), preparing the synthesis solution: The synthesis solution is prepared from silicon source, aluminum source, alkali source and deionized water; The silicon source is silica sol; the aluminum source is sodium aluminate; the alkali source is a mixture of sodium hydroxide and potassium hydroxide; the aluminum source and alkali source are added to deionized water, stirred until clear, then the silicon source is added, and aged to form a stable SiO2-Na2O-K2O-Al2O3-H2O synthesis solution system; Step (3), crystallization and film formation: The porous carrier coated with the T-type zeolite seed layer in step (1) is placed in the reactor, and the synthetic liquid that has been aged in step (2) is added to the reactor to completely immerse the porous carrier. After sealing the reactor, crystallization is performed to obtain the ERI type zeolite molecular sieve membrane. In step (2), the molar ratios of the components in the synthesis solution are as follows: the molar ratio of SiO2 to Al2O3 is (35-500):1; the molar ratio of H2O to SiO2 is (28-200):1; the molar ratio of Na2O to SiO2 is (0.3-1.5):1; the molar ratio of K2O to SiO2 is (0.01-0.3):1; the stirring and aging temperature is 10-40℃; and the aging time is 6-48h.

2. The method for preparing an ERI-type zeolite molecular sieve membrane according to claim 1, characterized in that, In step (1), the mass fraction of T-type zeolite seeds in molecular sieve seed solution A is 1.0-2.0 wt.%, and the particle size of the T-type zeolite seeds is 1.0-2.0 μm; The mass fraction of T-type zeolite seeds in molecular sieve seed solution B is 0.2-1.0 wt.%, and the particle size of the T-type zeolite seeds is 0.05-0.6 μm.

3. A method for preparing an ERI-type zeolite molecular sieve membrane according to claim 1 or 2, characterized in that, In step (1), the method of coating the molecular sieve seed liquid onto the surface of the porous carrier is impregnation, vacuum coating, wiping or spin coating.

4. A method for preparing an ERI-type zeolite molecular sieve membrane according to claim 1 or 2, characterized in that, In step (3), the crystallization temperature is 120-150℃ and the crystallization time is 3-6h.

5. A method for preparing an ERI-type zeolite molecular sieve membrane according to claim 1 or 2, characterized in that, In steps (1) and (3), the porous carrier is in the shape of a tube, a plate, or a hollow fiber.

6. The method for preparing an ERI-type zeolite molecular sieve membrane according to claim 5, characterized in that, In steps (1) and (3), the porous carrier is in the shape of a tubular carrier.

7. A method for preparing an ERI-type zeolite molecular sieve membrane according to claim 1 or 2, characterized in that, In steps (1) to (3), the porous carrier is made of alumina, zirconium oxide, mullite, stainless steel or metal mesh; the pore size of the porous carrier is 0.02-40 μm.

8. The method for preparing an ERI-type zeolite molecular sieve membrane according to claim 7, characterized in that, In steps (1) to (3), the porous carrier is made of alumina; the pore size of the porous carrier is 0.1-5 μm.

9. The ERI-type zeolite molecular sieve membrane prepared by any one of the preparation methods described in claims 1-8 is applied to the dehydration separation of organic solvents, wherein the organic solvent is acetic acid, ethanol, ethyl acetate or isopropanol.

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