Preparation method and application of ERI type zeolite molecular sieve membrane

Abstract

The invention belongs to the technical field of membrane separation materials, relates to a preparation method and application of an ERI type zeolite molecular sieve membrane, and provides a preparation method which is green, environment-friendly, simple in preparation process, rapid and economical. The method does not need to use an expensive organic template agent or inorganic fluorine ions harmful to the environment, is low in energy consumption, green and environment-friendly, the preparation process is simple and easy to operate, the repeatability is high, and the crystallization time is only 3-6 hours. The ERI type zeolite molecular sieve membrane prepared by the method shows excellent separation performance and good stability for dehydration and refining of organic solvents such as acetic acid. The preparation process provided by the invention is expected to provide a promising reference scheme for the preparation of the high-performance zeolite membrane, and has potential practical application feasibility.

Description

Technical Field

[0001] The invention belongs to the technical field of membrane separation materials and relates to a preparation method of an ERI type zeolite molecular sieve membrane and application thereof. Background Art

[0002] Acetic acid is one of the 50 most important chemicals in industry and is widely used in the synthesis of compounds such as polyvinyl acetate, vinyl acetate, acetate and chloroacetic acid. At the same time, acetic acid is also used as an important industrial solvent and raw material in textile printing and dyeing, photographic drug manufacturing and rubber industry. Whether it is the traditional methanol carbonyl synthesis method or the biomass fermentation method to prepare acetic acid, the dehydration and refining of crude acetic acid is an indispensable unit process. Although water and acetic acid usually do not form azeotropes, due to the presence of tangent pinch points in acetic acid solution, it is usually necessary to set up multiple equilibrium stages in the distillation tower and use a higher reflux ratio, which leads to increased energy consumption. Although the traditional acetic acid dehydration method is mature and widely used, it has the disadvantages of high energy consumption, large equipment investment and secondary pollution. Therefore, it is particularly important to develop new environmentally friendly and energy-saving acetic acid dehydration and separation technology.

[0003] Pervaporation is a membrane separation technology used to separate liquid mixtures. It can be used to selectively permeate water or organic compounds. Compared with traditional distillation technology, the pervaporation process not only overcomes the limitations of thermodynamic vapor-liquid equilibrium, but also only requires latent heat of evaporation, and has lower energy consumption. Pervaporation technology has many advantages such as simple and flexible operation, low energy consumption, high separation efficiency, no introduction of other reagents, no need for secondary treatment of products, no secondary pollution, and easy to scale up. It is particularly suitable for isomers, heat-sensitive, near-boiling and azeotropic systems that are difficult or impossible to separate by traditional separation methods. It is considered to be one of the most important and promising high-tech technologies in the current industrial technology transformation.

[0004] Since acetic acid is easily soluble in water, the miscible system of the two is relatively stable and difficult to separate from water. In addition, acetic acid is highly corrosive, and high requirements are also placed on the acid resistance of the material. In the 21st century, microporous inorganic membranes emerged as a new generation of membrane materials for separating molecular mixtures under harsh conditions. Since inorganic membranes have excellent acid resistance and adjustable hydrophilicity, they have great potential in the dehydration of acetic acid. Zeolite molecular sieve membranes are the largest family of inorganic pervaporation membrane materials, with adjustable hydrophilicity and sub-nanometer-sized molecular sieve pores, and provide strong preferential adsorption and rapid selective diffusion to achieve efficient molecular separation.

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

[0006] In addition, the acid resistance and hydrophilicity of zeolite membranes also depend on the topological structure of the zeolite membrane. Compared with medium-pore MFI and MOR zeolite membranes, ERI zeolites with small pores are eight-membered ring molecular sieves. Different topological structures are expected to show different acid resistance. ERI-configured molecular sieves can be divided into phosphorus-aluminum type (AlPO-17 and SAPO-17) and silicon-aluminum type according to the different skeleton components. The phosphorus-aluminum ERI molecular sieve skeleton is composed of Si, Al, P, and O atoms. The introduction of heterogeneous atoms P makes it more conducive to the adsorption of CO2, so it is often used as a CO2 adsorbent. The silicon-aluminum ERI molecular sieve is composed of skeleton Si, Al and O atoms. Compared with the phosphorus-aluminum ERI molecular sieve, the skeleton silicon content is higher. The higher the skeleton silicon content, the stronger the acid resistance, so its acid resistance and hydrothermal stability are more stable; and the silicon-aluminum ERI zeolite molecular sieve belongs to the medium silicon-aluminum ratio, which not only shows good acid resistance, but also maintains excellent hydrophilicity. This enables them to achieve high permeation flux while also having good acid-resistant separation selectivity and stability, and is suitable for dehydration separation applications in a variety of organic solvent systems. Therefore, the silicon-aluminum ERI zeolite membrane (hereinafter referred to as ERI zeolite membrane) is also a potential ideal membrane material for dehydration and refining of organic solvents such as acetic acid. However, there are currently no reports on the preparation of ERI zeolite membranes for dehydration and refining of organic solvents such as acetic acid. In addition, when designing the preparation process of ERI zeolite membranes, in order to ensure the feasibility and advantages in practical applications, higher requirements are also placed on the environmental protection issues, process complexity and economy of the preparation process. Summary of the invention

[0007] To solve the above problems, the present invention provides a method for preparing an ERI type zeolite molecular sieve membrane that is green, environmentally friendly, simple in preparation process, fast and economical, and is applied to the dehydration of organic solvents such as acetic acid. The preparation method proposed in the present invention does not require the use of expensive organic templates or inorganic fluoride ions that are harmful to the environment, has low energy consumption and is green and environmentally friendly, the preparation process is simple and easy to operate, has strong repeatability, and the crystallization time only takes 3-6 hours. The preparation process proposed in the present invention provides a promising reference scheme for the preparation of high-performance zeolite membranes, and has potential feasibility for practical application.

[0008] The technical solution of the present invention:

[0009] A method for preparing an ERI type zeolite molecular sieve membrane comprises coating T-type zeolite seed crystals on the surface of a porous carrier to form a flat and dense T-type zeolite seed crystal layer, preparing a synthetic liquid, and then hydrothermally crystallizing the coated T-type zeolite seed crystal layer in a synthetic liquid environment to form an ERI type zeolite membrane. The specific steps are as follows:

[0010] Step (1), coating a seed layer: dispersing two types of T-zeolite seeds with different particle sizes in deionized water respectively to obtain molecular sieve seed liquid A and molecular sieve seed liquid B; preheating a porous carrier at 150-200°C for 2-5 hours, and then coating the molecular sieve seed liquid A on the outer surface of the preheated porous carrier; curing at 150-200°C for 2-12 hours to obtain a flat and dense seed layer A1; wiping off loose seeds on the outer surface of the seed layer A1 with absorbent cotton; preheating the seed layer A1 at 80-120°C for 2-5 hours, and then coating the molecular sieve seed liquid B on the outer surface of the preheated seed layer A1; curing at 80-120°C for 2-12 hours to obtain a flat and dense T-zeolite seed layer;

[0011] Step (2), preparing a synthetic liquid: the synthetic liquid is prepared from a silicon source, an aluminum source, an 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 the alkali source are added to the deionized water, stirred until clarified, and then the silicon source is added, and aged to form a stable SiO2-Na2O-K2O-Al2O3-H2O synthetic liquid system;

[0012] Step (3), crystallization to form a membrane: the porous carrier coated with the T-type zeolite seed layer in step (1) is placed in a reactor, the synthetic liquid aged in step (2) is added to the reactor to completely immerse the porous carrier, and the reactor is sealed and crystallized to obtain an ERI-type zeolite molecular sieve membrane.

[0013] In the step (1), the mass fraction of the T-type zeolite seeds in the 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 the T-type zeolite seeds in the 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;

[0014] In step (1), the method for coating the molecular sieve seed solution on the surface of the porous carrier is dipping, hot dipping, two-step variable temperature hot dipping, vacuum coating, rubbing or spin coating; preferably, the two-step variable temperature hot dipping is used.

[0015] In the step (2), the molar ratio of the components of the synthetic liquid is: 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°C; and the aging time is 6-48h.

[0016] In the step (3), the crystallization temperature is 120-150° C. and the crystallization time is 3-6 hours.

[0017] In the steps (1) and (3), the porous carrier is in the shape of a tube, a flat plate, a hollow fiber or a multi-porous carrier; preferably a tubular carrier.

[0018] In steps (1) to (3), the material of the porous carrier is alumina, zirconia, mullite, stainless steel or metal mesh; the pore size of the porous carrier is 0.02-40 μm; preferably alumina, the pore size of the porous carrier is preferably 0.1-5 μm.

[0019] The ERI type zeolite molecular sieve membrane prepared by the above method is applied to dehydration separation of organic solvents, wherein the organic solvent is acetic acid, ethanol, ethyl acetate or isopropanol.

[0020] Beneficial effects of the present invention:

[0021] (1) The present invention provides a method for preparing an ERI type zeolite molecular sieve membrane. The preparation method does not require the use of expensive organic templates or inorganic fluoride ions that are harmful to the environment, has low energy consumption, and is green and environmentally friendly.

[0022] (2) The preparation process is simple and easy to operate, with strong repeatability, and the crystallization time is only 3-6 hours, which makes the method of the present invention have excellent film production efficiency.

[0023] (3) The ERI zeolite molecular sieve membrane prepared by the method of the present invention has excellent dehydration separation performance for organic solvents such as acetic acid. In addition, the ERI zeolite molecular sieve membrane prepared by the present invention not only exhibits high separation performance, but also exhibits good acid resistance and stability.

[0024] (4) The present invention effectively saves membrane production costs, significantly shortens membrane production cycles, and fully reflects the concept of green chemistry. The preparation process proposed in the present invention is expected to provide a promising reference scheme for the preparation of high-performance zeolite membranes and has potential feasibility for practical application. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is an X-ray diffraction pattern of the ERI zeolite molecular sieve membrane synthesized in Example 1;

[0026] Figure 2 is an X-ray diffraction pattern of the ERI type zeolite molecular sieve membrane synthesized in Example 2;

[0027] Figure 3 This is a surface scanning electron micrograph of the ERI zeolite molecular sieve membrane synthesized in Example 3;

[0028] Figure 4 is a cross-sectional scanning electron microscope image of the ERI type zeolite molecular sieve membrane synthesized in Example 3;

[0029] Figure 5 is an X-ray diffraction pattern of the ERI zeolite molecular sieve membrane synthesized in Example 3;

[0030] Figure 6 This is the pervaporation time stability of the ERI zeolite molecular sieve membrane synthesized in Example 3. DETAILED DESCRIPTION

[0031] The specific implementation of the present invention is further described below in conjunction with the accompanying drawings and technical solutions.

[0032] Example 1

[0033] (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 carrier A1; the seeds on the surface of the carrier were wiped off with absorbent cotton, and the seed layer carrier 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;

[0034] (2) preparing a synthetic solution with a molar ratio of 1SiO2:0.01Al2O3:1.5Na2O:0.1K2O:200H2O, stirring and aging at 10°C for 48h;

[0035] (3) Seal both ends of the coated T-shaped seed layer carrier tube and place it vertically in a reactor, add the aged synthetic liquid into the reactor to completely immerse the top of the carrier tube; seal the reactor and perform crystallization reaction at 130° C. for 4 hours;

[0036] (4) The synthesized zeolite molecular sieve membrane was washed with deionized water until it was neutral, and then dried in an oven at 50°C.

[0037] Depend on Figure 1 It can be seen that the zeolite molecular sieve membrane prepared in this example is a pure ERI zeolite crystal phase. The ERI zeolite molecular sieve membrane prepared in this example was subjected to a pervaporation test. At 60°C and 90°C, the fluxes for 90 wt.% acetic acid / water were 2.07 and 4.58 kg·m -2 ·h -1 , the separation factors are all greater than 10000. At 75°C, the fluxes for 70wt.%, 85wt.%, and 90wt.% acetic acid / water are 3.73, 3.03, and 2.82kg·m -2 ·h -1 , the separation factors are greater than 10000. At 75℃, the fluxes for 90wt.% ethanol / water and 90wt.% isopropanol / water are 3.81 and 5.43kg·m -2 ·h -1 , the separation factors are all greater than 10000.

[0038] Example 2

[0039] (1) The porous carrier tube was preheated at 200°C for 2 hours, and then quickly immersed in a T-type molecular sieve seed solution A with a mass concentration of 2.0wt.% and a particle size of 1.0μm, and cured at 200°C for 2 hours to obtain a seed layer carrier A1; the seeds on the surface of the carrier were wiped off with absorbent cotton, and the seed layer carrier A1 was preheated at 80°C for 2 hours, and then immersed in a T-type molecular sieve seed solution B with a mass concentration of 1.0wt.% and a particle size of 0.05μm, and cured at 80°C for 2 hours to obtain a flat and dense T-type zeolite seed layer;

[0040] (2) preparing a synthetic solution with a molar ratio of 1SiO2:0.002Al2O3:0.3Na2O:0.3K2O:28H2O, stirring and aging at 40°C for 6 h;

[0041] (3) Seal both ends of the coated T-shaped seed layer carrier tube and place it vertically in a reactor, add the aged synthetic liquid into the reactor to completely immerse the top of the carrier tube; seal the reactor and perform crystallization reaction at 120° C. for 6 hours;

[0042] (4) The synthesized zeolite molecular sieve membrane was washed with deionized water until it was neutral, and then dried in an oven at 50°C.

[0043] Depend on Figure 2 It can be seen that the main phase of the zeolite molecular sieve membrane prepared in this example is the ERI zeolite crystal phase, accompanied by a small amount of CHA zeolite crystal phase. The ERI zeolite molecular sieve membrane prepared in this example was subjected to a pervaporation test. At 60°C and 90°C, the fluxes for 90 wt.% acetic acid / water were 1.81 and 3.98 kg·m -2 ·h -1 , the separation factors are all greater than 10000. At 75°C, the fluxes for 70wt.%, 85wt.%, and 90wt.% acetic acid / water are 3.29, 2.77, and 2.57kg·m -2 ·h -1 , the separation factors are all greater than 10000. At 75°C, the fluxes for 90wt.% ethanol / water, 90wt.% ethyl acetate / water and 90wt.% isopropanol / water are 3.46, 5.89 and 5.04kg·m -2 ·h -1 , the separation factors are all greater than 10000.

[0044] Example 3

[0045] (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, and cured at 150° C. for 12 h to obtain a seed layer carrier A1; the seeds on the surface of the carrier were wiped off with absorbent cotton, and the seed layer carrier 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, and cured at 120° C. for 12 h to obtain a flat and dense T-type zeolite seed layer;

[0046] (2) preparing a synthetic solution with a molar ratio of 1SiO2:0.028Al2O3:0.8Na2O:0.01K2O:100H2O, stirring and aging at 25°C for 24 h;

[0047] (3) Seal both ends of the coated T-shaped seed layer carrier tube and place it vertically in a reactor, add the aged synthetic liquid into the reactor to completely immerse the top of the carrier tube; seal the reactor and perform crystallization reaction at 150° C. for 3 hours;

[0048] (4) The synthesized zeolite molecular sieve membrane was washed with deionized water until it was neutral, and then dried in an oven at 50°C.

[0049] Depend on Figure 3-5 It can be seen that the main phase of the zeolite molecular sieve membrane prepared in this example is the ERI zeolite crystal phase, accompanied by a small amount of CHA zeolite crystal phase. The ERI zeolite molecular sieve membrane prepared in this example was subjected to a pervaporation test. At 60°C and 90°C, the fluxes for 90 wt.% acetic acid / water were 2.47 and 5.40 kg·m -2 ·h -1 , the separation factors are all greater than 10000. At 75°C, the fluxes for 70wt.%, 85wt.% and 90wt.% acetic acid / water are 4.40, 3.58 and 3.32kg·m -2 ·h -1 , the separation factors are greater than 10000. At 75℃, the fluxes for 90wt.% ethanol / water and 90wt.% isopropanol / water are 4.48 and 6.39kg·m -2 ·h -1 , the separation factors are all greater than 10000.

[0050] Figure 6 The ERI zeolite molecular sieve membrane prepared for this embodiment is a test graph of the pervaporation time stability of 90wt.% acetic acid / water at 75°C. As can be seen from the figure, during the entire 154-hour pervaporation test, the separation factor of the ERI zeolite molecular sieve membrane remained basically stable, and the permeation flux first decreased and then remained stable. The reason for the slight decrease in the permeation flux may be that during the pervaporation separation process, acetic acid molecules are adsorbed on the membrane surface, occupying adsorption sites, causing water molecules to be unable to penetrate the membrane better. In the entire pervaporation time stability test, the ERI 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 a seed layer: dispersing two types of T-type zeolite seeds with different particle sizes in deionized water respectively to obtain molecular sieve seed liquid A and molecular sieve seed liquid B; preheating a porous carrier at 150-200°C for 2-5 hours, and then coating the molecular sieve seed liquid A on the outer surface of the preheated porous carrier; curing at 150-200°C for 2-12 hours to obtain a flat and dense seed layer A1; wiping off the loose seeds on the outer surface of the seed layer A1 with absorbent cotton; preheating the seed layer A1 at 80-120°C for 2-5 hours, and then coating the molecular sieve seed liquid B on the outer surface of the preheated seed layer A1; curing at 80-120°C for 2-12 hours to obtain a T-type zeolite seed layer; Step (2), preparing a synthetic liquid: the synthetic liquid is prepared from a silicon source, an aluminum source, an 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 the alkali source are added to deionized water, stirred until clarified, and then the silicon source is added, and aged to form a stable SiO2-Na2O-K2O-Al2O3-H2O synthetic liquid system; Step (3), crystallization to form a membrane: the porous carrier coated with the T-type zeolite seed layer in step (1) is placed in a reactor, the synthetic liquid aged in step (2) is added to the reactor to completely immerse the porous carrier, and the reactor is sealed and crystallized to obtain an ERI-type zeolite molecular sieve membrane.

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

3. The method for preparing an ERI type zeolite molecular sieve membrane according to claim 1 or 2, characterized in that: In the step (1), the method for coating the molecular sieve seed solution on the surface of the porous carrier is an impregnation method, a hot impregnation method, a two-step variable temperature hot impregnation method, a vacuum coating method, a wipe coating method or a spin coating method.

4. The method for preparing an ERI type zeolite molecular sieve membrane according to claim 1 or 2, characterized in that: In the step (2), the molar ratio of the components of the synthetic liquid is: 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°C; the aging time is 6-48h.

5. The method for preparing an ERI type zeolite molecular sieve membrane according to claim 1 or 2, characterized in that: In the step (3), the crystallization temperature is 120-150° C. and the crystallization time is 3-6 hours.

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

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

8. The method for preparing an ERI type zeolite molecular sieve membrane according to claim 1, 2 or 6, characterized in that: In the steps (1) to (3), the material of the porous carrier is alumina, zirconia, mullite, stainless steel or metal mesh; the pore size of the porous carrier is 0.02-40 μm.

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

10. The ERI zeolite molecular sieve membrane prepared by the preparation method according to any one of claims 1 to 9 is used for dehydration separation of an organic solvent, wherein the organic solvent is acetic acid, ethanol, ethyl acetate or isopropanol.

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